info201.github.io/r-intro.html at master · info201/info201.github.io · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang="">
<head>

  <meta charset="utf-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge" />
  <title>Chapter 5 Introduction to R | Technical Foundations of Informatics</title>
  <meta name="description" content="The course reader for INFO 201: Technical Foundations of Informatics." />
  <meta name="generator" content="bookdown 0.13 and GitBook 2.6.7" />

  <meta property="og:title" content="Chapter 5 Introduction to R | Technical Foundations of Informatics" />
  <meta property="og:type" content="book" />
  <meta property="og:url" content="https://info201.github.io/" />
  <meta property="og:image" content="https://info201.github.io/img/cover-img.png" />
  <meta property="og:description" content="The course reader for INFO 201: Technical Foundations of Informatics." />
  <meta name="github-repo" content="info201/book" />

  <meta name="twitter:card" content="summary" />
  <meta name="twitter:title" content="Chapter 5 Introduction to R | Technical Foundations of Informatics" />

  <meta name="twitter:description" content="The course reader for INFO 201: Technical Foundations of Informatics." />
  <meta name="twitter:image" content="https://info201.github.io/img/cover-img.png" />

<meta name="author" content="Michael Freeman and Joel Ross" />


<meta name="date" content="2019-09-11" />

  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <meta name="apple-mobile-web-app-capable" content="yes" />
  <meta name="apple-mobile-web-app-status-bar-style" content="black" />

  <link rel="shortcut icon" href="img/favicon.png" type="image/x-icon" />
<link rel="prev" href="git-basics.html"/>
<link rel="next" href="functions.html"/>
<script src="libs/jquery-2.2.3/jquery.min.js"></script>
<link href="libs/gitbook-2.6.7/css/style.css" rel="stylesheet" />
<link href="libs/gitbook-2.6.7/css/plugin-table.css" rel="stylesheet" />
<link href="libs/gitbook-2.6.7/css/plugin-bookdown.css" rel="stylesheet" />
<link href="libs/gitbook-2.6.7/css/plugin-highlight.css" rel="stylesheet" />
<link href="libs/gitbook-2.6.7/css/plugin-search.css" rel="stylesheet" />
<link href="libs/gitbook-2.6.7/css/plugin-fontsettings.css" rel="stylesheet" />


<script>
  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

  ga('create', 'UA-98444716-2', 'auto');
  ga('send', 'pageview');

</script>


<style type="text/css">
a.sourceLine { display: inline-block; line-height: 1.25; }
a.sourceLine { pointer-events: none; color: inherit; text-decoration: inherit; }
a.sourceLine:empty { height: 1.2em; }
.sourceCode { overflow: visible; }
code.sourceCode { white-space: pre; position: relative; }
pre.sourceCode { margin: 0; }
@media screen {
div.sourceCode { overflow: auto; }
}
@media print {
code.sourceCode { white-space: pre-wrap; }
a.sourceLine { text-indent: -1em; padding-left: 1em; }
}
pre.numberSource a.sourceLine
  { position: relative; left: -4em; }
pre.numberSource a.sourceLine::before
  { content: attr(data-line-number);
    position: relative; left: -1em; text-align: right; vertical-align: baseline;
    border: none; pointer-events: all; display: inline-block;
    -webkit-touch-callout: none; -webkit-user-select: none;
    -khtml-user-select: none; -moz-user-select: none;
    -ms-user-select: none; user-select: none;
    padding: 0 4px; width: 4em;
    color: #aaaaaa;
  }
pre.numberSource { margin-left: 3em; border-left: 1px solid #aaaaaa;  padding-left: 4px; }
div.sourceCode
  {  }
@media screen {
a.sourceLine::before { text-decoration: underline; }
}
code span.al { color: #ff0000; font-weight: bold; } /* Alert */
code span.an { color: #60a0b0; font-weight: bold; font-style: italic; } /* Annotation */
code span.at { color: #7d9029; } /* Attribute */
code span.bn { color: #40a070; } /* BaseN */
code span.bu { } /* BuiltIn */
code span.cf { color: #007020; font-weight: bold; } /* ControlFlow */
code span.ch { color: #4070a0; } /* Char */
code span.cn { color: #880000; } /* Constant */
code span.co { color: #60a0b0; font-style: italic; } /* Comment */
code span.cv { color: #60a0b0; font-weight: bold; font-style: italic; } /* CommentVar */
code span.do { color: #ba2121; font-style: italic; } /* Documentation */
code span.dt { color: #902000; } /* DataType */
code span.dv { color: #40a070; } /* DecVal */
code span.er { color: #ff0000; font-weight: bold; } /* Error */
code span.ex { } /* Extension */
code span.fl { color: #40a070; } /* Float */
code span.fu { color: #06287e; } /* Function */
code span.im { } /* Import */
code span.in { color: #60a0b0; font-weight: bold; font-style: italic; } /* Information */
code span.kw { color: #007020; font-weight: bold; } /* Keyword */
code span.op { color: #666666; } /* Operator */
code span.ot { color: #007020; } /* Other */
code span.pp { color: #bc7a00; } /* Preprocessor */
code span.sc { color: #4070a0; } /* SpecialChar */
code span.ss { color: #bb6688; } /* SpecialString */
code span.st { color: #4070a0; } /* String */
code span.va { color: #19177c; } /* Variable */
code span.vs { color: #4070a0; } /* VerbatimString */
code span.wa { color: #60a0b0; font-weight: bold; font-style: italic; } /* Warning */
</style>

<link rel="stylesheet" href="css/style.css" type="text/css" />
</head>

<body>


  <div class="book without-animation with-summary font-size-2 font-family-1" data-basepath=".">

    <div class="book-summary">
      <nav role="navigation">

<ul class="summary">
<li><a href="./">Technical Foundations of Informatics</a></li>

<li class="divider"></li>
<li class="chapter" data-level="" data-path="index.html"><a href="index.html"><i class="fa fa-check"></i>About the Book</a></li>
<li class="chapter" data-level="1" data-path="setup-machine.html"><a href="setup-machine.html"><i class="fa fa-check"></i><b>1</b> Setting up your Machine</a><ul>
<li class="chapter" data-level="1.1" data-path="setup-machine.html"><a href="setup-machine.html#git"><i class="fa fa-check"></i><b>1.1</b> Git</a><ul>
<li class="chapter" data-level="1.1.1" data-path="setup-machine.html"><a href="setup-machine.html#github"><i class="fa fa-check"></i><b>1.1.1</b> GitHub</a></li>
</ul></li>
<li class="chapter" data-level="1.2" data-path="setup-machine.html"><a href="setup-machine.html#command-line-tools-bash"><i class="fa fa-check"></i><b>1.2</b> Command-line Tools (Bash)</a><ul>
<li class="chapter" data-level="1.2.1" data-path="setup-machine.html"><a href="setup-machine.html#command-line-on-a-mac"><i class="fa fa-check"></i><b>1.2.1</b> Command-line on a Mac</a></li>
<li class="chapter" data-level="1.2.2" data-path="setup-machine.html"><a href="setup-machine.html#command-line-on-windows"><i class="fa fa-check"></i><b>1.2.2</b> Command-line on Windows</a></li>
</ul></li>
<li class="chapter" data-level="1.3" data-path="setup-machine.html"><a href="setup-machine.html#text-editors"><i class="fa fa-check"></i><b>1.3</b> Text Editors</a><ul>
<li class="chapter" data-level="1.3.1" data-path="setup-machine.html"><a href="setup-machine.html#atom"><i class="fa fa-check"></i><b>1.3.1</b> Atom</a></li>
<li class="chapter" data-level="1.3.2" data-path="setup-machine.html"><a href="setup-machine.html#visual-studio-code"><i class="fa fa-check"></i><b>1.3.2</b> Visual Studio Code</a></li>
<li class="chapter" data-level="1.3.3" data-path="setup-machine.html"><a href="setup-machine.html#sublime-text"><i class="fa fa-check"></i><b>1.3.3</b> Sublime Text</a></li>
</ul></li>
<li class="chapter" data-level="1.4" data-path="setup-machine.html"><a href="setup-machine.html#r-language"><i class="fa fa-check"></i><b>1.4</b> R Language</a></li>
<li class="chapter" data-level="1.5" data-path="setup-machine.html"><a href="setup-machine.html#rstudio"><i class="fa fa-check"></i><b>1.5</b> RStudio</a></li>
<li class="chapter" data-level="" data-path="setup-machine.html"><a href="setup-machine.html#resources"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="2" data-path="command-line.html"><a href="command-line.html"><i class="fa fa-check"></i><b>2</b> The Command Line</a><ul>
<li class="chapter" data-level="2.1" data-path="command-line.html"><a href="command-line.html#accessing-the-command-line"><i class="fa fa-check"></i><b>2.1</b> Accessing the Command-Line</a></li>
<li class="chapter" data-level="2.2" data-path="command-line.html"><a href="command-line.html#navigating-the-command-line"><i class="fa fa-check"></i><b>2.2</b> Navigating the Command Line</a><ul>
<li class="chapter" data-level="2.2.1" data-path="command-line.html"><a href="command-line.html#changing-directories"><i class="fa fa-check"></i><b>2.2.1</b> Changing Directories</a></li>
<li class="chapter" data-level="2.2.2" data-path="command-line.html"><a href="command-line.html#listing-files"><i class="fa fa-check"></i><b>2.2.2</b> Listing Files</a></li>
<li class="chapter" data-level="2.2.3" data-path="command-line.html"><a href="command-line.html#paths"><i class="fa fa-check"></i><b>2.2.3</b> Paths</a></li>
</ul></li>
<li class="chapter" data-level="2.3" data-path="command-line.html"><a href="command-line.html#file-commands"><i class="fa fa-check"></i><b>2.3</b> File Commands</a><ul>
<li class="chapter" data-level="2.3.1" data-path="command-line.html"><a href="command-line.html#learning-new-commands"><i class="fa fa-check"></i><b>2.3.1</b> Learning New Commands</a></li>
</ul></li>
<li class="chapter" data-level="2.4" data-path="command-line.html"><a href="command-line.html#dealing-with-errors"><i class="fa fa-check"></i><b>2.4</b> Dealing With Errors</a></li>
<li class="chapter" data-level="" data-path="command-line.html"><a href="command-line.html#resources-1"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="3" data-path="markdown.html"><a href="markdown.html"><i class="fa fa-check"></i><b>3</b> Markdown</a><ul>
<li class="chapter" data-level="3.1" data-path="markdown.html"><a href="markdown.html#writing-markdown"><i class="fa fa-check"></i><b>3.1</b> Writing Markdown</a><ul>
<li class="chapter" data-level="3.1.1" data-path="markdown.html"><a href="markdown.html#text-formatting"><i class="fa fa-check"></i><b>3.1.1</b> Text Formatting</a></li>
<li class="chapter" data-level="3.1.2" data-path="markdown.html"><a href="markdown.html#text-blocks"><i class="fa fa-check"></i><b>3.1.2</b> Text Blocks</a></li>
</ul></li>
<li class="chapter" data-level="3.2" data-path="markdown.html"><a href="markdown.html#rendering-markdown"><i class="fa fa-check"></i><b>3.2</b> Rendering Markdown</a></li>
<li class="chapter" data-level="" data-path="markdown.html"><a href="markdown.html#resources-2"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="4" data-path="git-basics.html"><a href="git-basics.html"><i class="fa fa-check"></i><b>4</b> Git and GitHub</a><ul>
<li class="chapter" data-level="4.1" data-path="git-basics.html"><a href="git-basics.html#what-is-this-git-thing-anyway"><i class="fa fa-check"></i><b>4.1</b> What is this <em>git</em> thing anyway?</a><ul>
<li class="chapter" data-level="4.1.1" data-path="git-basics.html"><a href="git-basics.html#git-core-concepts"><i class="fa fa-check"></i><b>4.1.1</b> Git Core Concepts</a></li>
<li class="chapter" data-level="4.1.2" data-path="git-basics.html"><a href="git-basics.html#wait-but-what-is-github-then"><i class="fa fa-check"></i><b>4.1.2</b> Wait, but what is GitHub then?</a></li>
</ul></li>
<li class="chapter" data-level="4.2" data-path="git-basics.html"><a href="git-basics.html#installation-setup"><i class="fa fa-check"></i><b>4.2</b> Installation &amp; Setup</a><ul>
<li class="chapter" data-level="4.2.1" data-path="git-basics.html"><a href="git-basics.html#creating-a-repo"><i class="fa fa-check"></i><b>4.2.1</b> Creating a Repo</a></li>
<li class="chapter" data-level="4.2.2" data-path="git-basics.html"><a href="git-basics.html#checking-status"><i class="fa fa-check"></i><b>4.2.2</b> Checking Status</a></li>
</ul></li>
<li class="chapter" data-level="4.3" data-path="git-basics.html"><a href="git-basics.html#making-changes"><i class="fa fa-check"></i><b>4.3</b> Making Changes</a><ul>
<li class="chapter" data-level="4.3.1" data-path="git-basics.html"><a href="git-basics.html#adding-files"><i class="fa fa-check"></i><b>4.3.1</b> Adding Files</a></li>
<li class="chapter" data-level="4.3.2" data-path="git-basics.html"><a href="git-basics.html#committing"><i class="fa fa-check"></i><b>4.3.2</b> Committing</a></li>
<li class="chapter" data-level="4.3.3" data-path="git-basics.html"><a href="git-basics.html#commit-history"><i class="fa fa-check"></i><b>4.3.3</b> Commit History</a></li>
<li class="chapter" data-level="4.3.4" data-path="git-basics.html"><a href="git-basics.html#reviewing-the-process"><i class="fa fa-check"></i><b>4.3.4</b> Reviewing the Process</a></li>
<li class="chapter" data-level="4.3.5" data-path="git-basics.html"><a href="git-basics.html#gitignore"><i class="fa fa-check"></i><b>4.3.5</b> The <code>.gitignore</code> File</a></li>
</ul></li>
<li class="chapter" data-level="4.4" data-path="git-basics.html"><a href="git-basics.html#github-and-remotes"><i class="fa fa-check"></i><b>4.4</b> GitHub and Remotes</a><ul>
<li class="chapter" data-level="4.4.1" data-path="git-basics.html"><a href="git-basics.html#forking-and-cloning"><i class="fa fa-check"></i><b>4.4.1</b> Forking and Cloning</a></li>
<li class="chapter" data-level="4.4.2" data-path="git-basics.html"><a href="git-basics.html#pushing-and-pulling"><i class="fa fa-check"></i><b>4.4.2</b> Pushing and Pulling</a></li>
<li class="chapter" data-level="4.4.3" data-path="git-basics.html"><a href="git-basics.html#reviewing-the-process-1"><i class="fa fa-check"></i><b>4.4.3</b> Reviewing The Process</a></li>
</ul></li>
<li class="chapter" data-level="4.5" data-path="git-basics.html"><a href="git-basics.html#course-assignments-on-github"><i class="fa fa-check"></i><b>4.5</b> Course Assignments on GitHub</a></li>
<li class="chapter" data-level="4.6" data-path="git-basics.html"><a href="git-basics.html#command-summary"><i class="fa fa-check"></i><b>4.6</b> Command Summary</a></li>
<li class="chapter" data-level="" data-path="git-basics.html"><a href="git-basics.html#resources-3"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="5" data-path="r-intro.html"><a href="r-intro.html"><i class="fa fa-check"></i><b>5</b> Introduction to R</a><ul>
<li class="chapter" data-level="5.1" data-path="r-intro.html"><a href="r-intro.html#programming-with-r"><i class="fa fa-check"></i><b>5.1</b> Programming with R</a></li>
<li class="chapter" data-level="5.2" data-path="r-intro.html"><a href="r-intro.html#running-r-scripts"><i class="fa fa-check"></i><b>5.2</b> Running R Scripts</a><ul>
<li class="chapter" data-level="5.2.1" data-path="r-intro.html"><a href="r-intro.html#running-r-cmd"><i class="fa fa-check"></i><b>5.2.1</b> Command-Line</a></li>
<li class="chapter" data-level="5.2.2" data-path="r-intro.html"><a href="r-intro.html#running-r-rstudio"><i class="fa fa-check"></i><b>5.2.2</b> RStudio</a></li>
</ul></li>
<li class="chapter" data-level="5.3" data-path="r-intro.html"><a href="r-intro.html#comments"><i class="fa fa-check"></i><b>5.3</b> Comments</a></li>
<li class="chapter" data-level="5.4" data-path="r-intro.html"><a href="r-intro.html#variables"><i class="fa fa-check"></i><b>5.4</b> Variables</a><ul>
<li class="chapter" data-level="5.4.1" data-path="r-intro.html"><a href="r-intro.html#basic-data-types"><i class="fa fa-check"></i><b>5.4.1</b> Basic Data Types</a></li>
</ul></li>
<li class="chapter" data-level="5.5" data-path="r-intro.html"><a href="r-intro.html#gettinghelp"><i class="fa fa-check"></i><b>5.5</b> Getting Help</a></li>
<li class="chapter" data-level="" data-path="r-intro.html"><a href="r-intro.html#resources-4"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="6" data-path="functions.html"><a href="functions.html"><i class="fa fa-check"></i><b>6</b> Functions</a><ul>
<li class="chapter" data-level="6.1" data-path="functions.html"><a href="functions.html#what-are-functions"><i class="fa fa-check"></i><b>6.1</b> What are Functions?</a></li>
<li class="chapter" data-level="6.2" data-path="functions.html"><a href="functions.html#how-to-use-functions"><i class="fa fa-check"></i><b>6.2</b> How to Use Functions</a></li>
<li class="chapter" data-level="6.3" data-path="functions.html"><a href="functions.html#built-in-r-functions"><i class="fa fa-check"></i><b>6.3</b> Built-in R Functions</a></li>
<li class="chapter" data-level="6.4" data-path="functions.html"><a href="functions.html#loading-functions"><i class="fa fa-check"></i><b>6.4</b> Loading Functions</a></li>
<li class="chapter" data-level="6.5" data-path="functions.html"><a href="functions.html#writing-functions"><i class="fa fa-check"></i><b>6.5</b> Writing Functions</a></li>
<li class="chapter" data-level="6.6" data-path="functions.html"><a href="functions.html#conditional-statements"><i class="fa fa-check"></i><b>6.6</b> Conditional Statements</a></li>
<li class="chapter" data-level="" data-path="functions.html"><a href="functions.html#resources-5"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="7" data-path="vectors.html"><a href="vectors.html"><i class="fa fa-check"></i><b>7</b> Vectors</a><ul>
<li class="chapter" data-level="7.1" data-path="vectors.html"><a href="vectors.html#what-is-a-vector"><i class="fa fa-check"></i><b>7.1</b> What is a Vector?</a></li>
<li class="chapter" data-level="7.2" data-path="vectors.html"><a href="vectors.html#creating-vectors"><i class="fa fa-check"></i><b>7.2</b> Creating Vectors</a></li>
<li class="chapter" data-level="7.3" data-path="vectors.html"><a href="vectors.html#vector-indices"><i class="fa fa-check"></i><b>7.3</b> Vector Indices</a><ul>
<li class="chapter" data-level="7.3.1" data-path="vectors.html"><a href="vectors.html#simple-numeric-indices"><i class="fa fa-check"></i><b>7.3.1</b> Simple Numeric Indices</a></li>
<li class="chapter" data-level="7.3.2" data-path="vectors.html"><a href="vectors.html#multiple-indices"><i class="fa fa-check"></i><b>7.3.2</b> Multiple Indices</a></li>
<li class="chapter" data-level="7.3.3" data-path="vectors.html"><a href="vectors.html#logical-indexing"><i class="fa fa-check"></i><b>7.3.3</b> Logical Indexing</a></li>
<li class="chapter" data-level="7.3.4" data-path="vectors.html"><a href="vectors.html#named-vectors-and-character-indexing"><i class="fa fa-check"></i><b>7.3.4</b> Named Vectors and Character Indexing</a></li>
</ul></li>
<li class="chapter" data-level="7.4" data-path="vectors.html"><a href="vectors.html#modifying-vectors"><i class="fa fa-check"></i><b>7.4</b> Modifying Vectors</a></li>
<li class="chapter" data-level="7.5" data-path="vectors.html"><a href="vectors.html#vectorized-operations"><i class="fa fa-check"></i><b>7.5</b> Vectorized Operations</a><ul>
<li class="chapter" data-level="7.5.1" data-path="vectors.html"><a href="vectors.html#vectorized-operators"><i class="fa fa-check"></i><b>7.5.1</b> Vectorized Operators</a></li>
<li class="chapter" data-level="7.5.2" data-path="vectors.html"><a href="vectors.html#vectorized-functions"><i class="fa fa-check"></i><b>7.5.2</b> Vectorized Functions</a></li>
<li class="chapter" data-level="7.5.3" data-path="vectors.html"><a href="vectors.html#recycling"><i class="fa fa-check"></i><b>7.5.3</b> Recycling</a></li>
<li class="chapter" data-level="7.5.4" data-path="vectors.html"><a href="vectors.html#r-is-a-vectorized-world"><i class="fa fa-check"></i><b>7.5.4</b> R Is a Vectorized World</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="vectors.html"><a href="vectors.html#resources-6"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="8" data-path="lists.html"><a href="lists.html"><i class="fa fa-check"></i><b>8</b> Lists</a><ul>
<li class="chapter" data-level="8.1" data-path="lists.html"><a href="lists.html#what-is-a-list"><i class="fa fa-check"></i><b>8.1</b> What is a List?</a></li>
<li class="chapter" data-level="8.2" data-path="lists.html"><a href="lists.html#creating-lists"><i class="fa fa-check"></i><b>8.2</b> Creating Lists</a></li>
<li class="chapter" data-level="8.3" data-path="lists.html"><a href="lists.html#accessing-list-elements"><i class="fa fa-check"></i><b>8.3</b> Accessing List Elements</a><ul>
<li class="chapter" data-level="8.3.1" data-path="lists.html"><a href="lists.html#lists-indexing-by-position"><i class="fa fa-check"></i><b>8.3.1</b> Indexing by position</a></li>
<li class="chapter" data-level="8.3.2" data-path="lists.html"><a href="lists.html#indexing-by-name"><i class="fa fa-check"></i><b>8.3.2</b> Indexing by Name</a></li>
<li class="chapter" data-level="8.3.3" data-path="lists.html"><a href="lists.html#indexing-by-logical-vector"><i class="fa fa-check"></i><b>8.3.3</b> Indexing by Logical Vector</a></li>
<li class="chapter" data-level="8.3.4" data-path="lists.html"><a href="lists.html#lists-dollar-shortcut"><i class="fa fa-check"></i><b>8.3.4</b> Extracting named elements with <code>$</code></a></li>
<li class="chapter" data-level="8.3.5" data-path="lists.html"><a href="lists.html#single-vs.double-brackets-vs.dollar"><i class="fa fa-check"></i><b>8.3.5</b> Single vs. Double Brackets vs. Dollar</a></li>
</ul></li>
<li class="chapter" data-level="8.4" data-path="lists.html"><a href="lists.html#modifying-lists"><i class="fa fa-check"></i><b>8.4</b> Modifying Lists</a></li>
<li class="chapter" data-level="8.5" data-path="lists.html"><a href="lists.html#the-lapply-function"><i class="fa fa-check"></i><b>8.5</b> The <code>lapply()</code> Function</a></li>
<li class="chapter" data-level="" data-path="lists.html"><a href="lists.html#resources-7"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="9" data-path="data-frames.html"><a href="data-frames.html"><i class="fa fa-check"></i><b>9</b> Data Frames</a><ul>
<li class="chapter" data-level="9.1" data-path="data-frames.html"><a href="data-frames.html#what-is-a-data-frame"><i class="fa fa-check"></i><b>9.1</b> What is a Data Frame?</a><ul>
<li class="chapter" data-level="9.1.1" data-path="data-frames.html"><a href="data-frames.html#creating-data-frames"><i class="fa fa-check"></i><b>9.1.1</b> Creating Data Frames</a></li>
<li class="chapter" data-level="9.1.2" data-path="data-frames.html"><a href="data-frames.html#describing-structure-of-data-frames"><i class="fa fa-check"></i><b>9.1.2</b> Describing Structure of Data Frames</a></li>
<li class="chapter" data-level="9.1.3" data-path="data-frames.html"><a href="data-frames.html#accessing-data-in-data-frames"><i class="fa fa-check"></i><b>9.1.3</b> Accessing Data in Data Frames</a></li>
</ul></li>
<li class="chapter" data-level="9.2" data-path="data-frames.html"><a href="data-frames.html#csv-files"><i class="fa fa-check"></i><b>9.2</b> Working with CSV Data</a><ul>
<li class="chapter" data-level="9.2.1" data-path="data-frames.html"><a href="data-frames.html#working-directory"><i class="fa fa-check"></i><b>9.2.1</b> Working Directory</a></li>
</ul></li>
<li class="chapter" data-level="9.3" data-path="data-frames.html"><a href="data-frames.html#factors"><i class="fa fa-check"></i><b>9.3</b> Factor Variables</a></li>
<li class="chapter" data-level="" data-path="data-frames.html"><a href="data-frames.html#resources-8"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="10" data-path="dplyr.html"><a href="dplyr.html"><i class="fa fa-check"></i><b>10</b> The <code>dplyr</code> Library</a><ul>
<li class="chapter" data-level="10.1" data-path="dplyr.html"><a href="dplyr.html#a-grammar-of-data-manipulation"><i class="fa fa-check"></i><b>10.1</b> A Grammar of Data Manipulation</a></li>
<li class="chapter" data-level="10.2" data-path="dplyr.html"><a href="dplyr.html#using-dplyr-functions"><i class="fa fa-check"></i><b>10.2</b> Using <code>dplyr</code> Functions</a><ul>
<li class="chapter" data-level="10.2.1" data-path="dplyr.html"><a href="dplyr.html#select"><i class="fa fa-check"></i><b>10.2.1</b> Select</a></li>
<li class="chapter" data-level="10.2.2" data-path="dplyr.html"><a href="dplyr.html#filter"><i class="fa fa-check"></i><b>10.2.2</b> Filter</a></li>
<li class="chapter" data-level="10.2.3" data-path="dplyr.html"><a href="dplyr.html#mutate"><i class="fa fa-check"></i><b>10.2.3</b> Mutate</a></li>
<li class="chapter" data-level="10.2.4" data-path="dplyr.html"><a href="dplyr.html#arrange"><i class="fa fa-check"></i><b>10.2.4</b> Arrange</a></li>
<li class="chapter" data-level="10.2.5" data-path="dplyr.html"><a href="dplyr.html#summarize"><i class="fa fa-check"></i><b>10.2.5</b> Summarize</a></li>
<li class="chapter" data-level="10.2.6" data-path="dplyr.html"><a href="dplyr.html#distinct"><i class="fa fa-check"></i><b>10.2.6</b> Distinct</a></li>
</ul></li>
<li class="chapter" data-level="10.3" data-path="dplyr.html"><a href="dplyr.html#multiple-operations"><i class="fa fa-check"></i><b>10.3</b> Multiple Operations</a><ul>
<li class="chapter" data-level="10.3.1" data-path="dplyr.html"><a href="dplyr.html#the-pipe-operator"><i class="fa fa-check"></i><b>10.3.1</b> The Pipe Operator</a></li>
</ul></li>
<li class="chapter" data-level="10.4" data-path="dplyr.html"><a href="dplyr.html#grouped-operations"><i class="fa fa-check"></i><b>10.4</b> Grouped Operations</a></li>
<li class="chapter" data-level="10.5" data-path="dplyr.html"><a href="dplyr.html#joins"><i class="fa fa-check"></i><b>10.5</b> Joins</a></li>
<li class="chapter" data-level="10.6" data-path="dplyr.html"><a href="dplyr.html#non-standard-evaluation-vs.standard-evaluation"><i class="fa fa-check"></i><b>10.6</b> Non-Standard Evaluation vs. Standard Evaluation</a><ul>
<li class="chapter" data-level="10.6.1" data-path="dplyr.html"><a href="dplyr.html#explicit-standard-evaluation"><i class="fa fa-check"></i><b>10.6.1</b> Explicit Standard Evaluation</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="dplyr.html"><a href="dplyr.html#resources-9"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="11" data-path="apis.html"><a href="apis.html"><i class="fa fa-check"></i><b>11</b> Accessing Web APIs</a><ul>
<li class="chapter" data-level="11.1" data-path="apis.html"><a href="apis.html#what-is-a-web-api"><i class="fa fa-check"></i><b>11.1</b> What is a Web API?</a></li>
<li class="chapter" data-level="11.2" data-path="apis.html"><a href="apis.html#restful-requests"><i class="fa fa-check"></i><b>11.2</b> RESTful Requests</a><ul>
<li class="chapter" data-level="11.2.1" data-path="apis.html"><a href="apis.html#uris"><i class="fa fa-check"></i><b>11.2.1</b> URIs</a></li>
<li class="chapter" data-level="11.2.2" data-path="apis.html"><a href="apis.html#http-verbs"><i class="fa fa-check"></i><b>11.2.2</b> HTTP Verbs</a></li>
</ul></li>
<li class="chapter" data-level="11.3" data-path="apis.html"><a href="apis.html#accessing-web-apis"><i class="fa fa-check"></i><b>11.3</b> Accessing Web APIs</a></li>
<li class="chapter" data-level="11.4" data-path="apis.html"><a href="apis.html#json"><i class="fa fa-check"></i><b>11.4</b> JSON Data</a><ul>
<li class="chapter" data-level="11.4.1" data-path="apis.html"><a href="apis.html#parsing-json"><i class="fa fa-check"></i><b>11.4.1</b> Parsing JSON</a></li>
<li class="chapter" data-level="11.4.2" data-path="apis.html"><a href="apis.html#flattening-data"><i class="fa fa-check"></i><b>11.4.2</b> Flattening Data</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="apis.html"><a href="apis.html#resources-10"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="12" data-path="r-markdown.html"><a href="r-markdown.html"><i class="fa fa-check"></i><b>12</b> R Markdown</a><ul>
<li class="chapter" data-level="12.1" data-path="r-markdown.html"><a href="r-markdown.html#r-markdown-and-rstudio"><i class="fa fa-check"></i><b>12.1</b> R Markdown and RStudio</a><ul>
<li class="chapter" data-level="12.1.1" data-path="r-markdown.html"><a href="r-markdown.html#creating-.rmd-files"><i class="fa fa-check"></i><b>12.1.1</b> Creating <code>.Rmd</code> Files</a></li>
<li class="chapter" data-level="12.1.2" data-path="r-markdown.html"><a href="r-markdown.html#rmd-content"><i class="fa fa-check"></i><b>12.1.2</b> <code>.Rmd</code> Content</a></li>
<li class="chapter" data-level="12.1.3" data-path="r-markdown.html"><a href="r-markdown.html#knitting-documents"><i class="fa fa-check"></i><b>12.1.3</b> Knitting Documents</a></li>
<li class="chapter" data-level="12.1.4" data-path="r-markdown.html"><a href="r-markdown.html#html"><i class="fa fa-check"></i><b>12.1.4</b> HTML</a></li>
</ul></li>
<li class="chapter" data-level="12.2" data-path="r-markdown.html"><a href="r-markdown.html#r-markdown-syntax"><i class="fa fa-check"></i><b>12.2</b> R Markdown Syntax</a><ul>
<li class="chapter" data-level="12.2.1" data-path="r-markdown.html"><a href="r-markdown.html#r-code-chunks"><i class="fa fa-check"></i><b>12.2.1</b> R Code Chunks</a></li>
<li class="chapter" data-level="12.2.2" data-path="r-markdown.html"><a href="r-markdown.html#inline-code"><i class="fa fa-check"></i><b>12.2.2</b> Inline Code</a></li>
</ul></li>
<li class="chapter" data-level="12.3" data-path="r-markdown.html"><a href="r-markdown.html#rendering-data"><i class="fa fa-check"></i><b>12.3</b> Rendering Data</a><ul>
<li class="chapter" data-level="12.3.1" data-path="r-markdown.html"><a href="r-markdown.html#rendering-strings"><i class="fa fa-check"></i><b>12.3.1</b> Rendering Strings</a></li>
<li class="chapter" data-level="12.3.2" data-path="r-markdown.html"><a href="r-markdown.html#rendering-lists"><i class="fa fa-check"></i><b>12.3.2</b> Rendering Lists</a></li>
<li class="chapter" data-level="12.3.3" data-path="r-markdown.html"><a href="r-markdown.html#rendering-tables"><i class="fa fa-check"></i><b>12.3.3</b> Rendering Tables</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="r-markdown.html"><a href="r-markdown.html#resources-11"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="13" data-path="ggplot2.html"><a href="ggplot2.html"><i class="fa fa-check"></i><b>13</b> The <code>gglot2</code> Library</a><ul>
<li class="chapter" data-level="13.1" data-path="ggplot2.html"><a href="ggplot2.html#a-grammar-of-graphics"><i class="fa fa-check"></i><b>13.1</b> A Grammar of Graphics</a></li>
<li class="chapter" data-level="13.2" data-path="ggplot2.html"><a href="ggplot2.html#basic-plotting-with-ggplot2"><i class="fa fa-check"></i><b>13.2</b> Basic Plotting with <code>ggplot2</code></a><ul>
<li class="chapter" data-level="13.2.1" data-path="ggplot2.html"><a href="ggplot2.html#ggplot2-library"><i class="fa fa-check"></i><b>13.2.1</b> <em>ggplot2</em> library</a></li>
<li class="chapter" data-level="13.2.2" data-path="ggplot2.html"><a href="ggplot2.html#mpg-data"><i class="fa fa-check"></i><b>13.2.2</b> <em>mpg</em> data</a></li>
<li class="chapter" data-level="13.2.3" data-path="ggplot2.html"><a href="ggplot2.html#our-first-ggplot"><i class="fa fa-check"></i><b>13.2.3</b> Our first ggplot</a></li>
<li class="chapter" data-level="13.2.4" data-path="ggplot2.html"><a href="ggplot2.html#aesthetic-mappings"><i class="fa fa-check"></i><b>13.2.4</b> Aesthetic Mappings</a></li>
</ul></li>
<li class="chapter" data-level="13.3" data-path="ggplot2.html"><a href="ggplot2.html#complex-plots"><i class="fa fa-check"></i><b>13.3</b> Complex Plots</a><ul>
<li class="chapter" data-level="13.3.1" data-path="ggplot2.html"><a href="ggplot2.html#specifying-geometry"><i class="fa fa-check"></i><b>13.3.1</b> Specifying Geometry</a></li>
<li class="chapter" data-level="13.3.2" data-path="ggplot2.html"><a href="ggplot2.html#styling-with-scales"><i class="fa fa-check"></i><b>13.3.2</b> Styling with Scales</a></li>
<li class="chapter" data-level="13.3.3" data-path="ggplot2.html"><a href="ggplot2.html#coordinate-systems"><i class="fa fa-check"></i><b>13.3.3</b> Coordinate Systems</a></li>
<li class="chapter" data-level="13.3.4" data-path="ggplot2.html"><a href="ggplot2.html#facets"><i class="fa fa-check"></i><b>13.3.4</b> Facets</a></li>
<li class="chapter" data-level="13.3.5" data-path="ggplot2.html"><a href="ggplot2.html#labels-annotations"><i class="fa fa-check"></i><b>13.3.5</b> Labels &amp; Annotations</a></li>
</ul></li>
<li class="chapter" data-level="13.4" data-path="ggplot2.html"><a href="ggplot2.html#plotting-in-scripts"><i class="fa fa-check"></i><b>13.4</b> Plotting in Scripts</a></li>
<li class="chapter" data-level="13.5" data-path="ggplot2.html"><a href="ggplot2.html#other-visualization-libraries"><i class="fa fa-check"></i><b>13.5</b> Other Visualization Libraries</a></li>
<li class="chapter" data-level="" data-path="ggplot2.html"><a href="ggplot2.html#resources-12"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="14" data-path="git-branches.html"><a href="git-branches.html"><i class="fa fa-check"></i><b>14</b> Git Branches</a><ul>
<li class="chapter" data-level="14.1" data-path="git-branches.html"><a href="git-branches.html#git-branches-1"><i class="fa fa-check"></i><b>14.1</b> Git Branches</a></li>
<li class="chapter" data-level="14.2" data-path="git-branches.html"><a href="git-branches.html#merging"><i class="fa fa-check"></i><b>14.2</b> Merging</a><ul>
<li class="chapter" data-level="14.2.1" data-path="git-branches.html"><a href="git-branches.html#merge-conflicts"><i class="fa fa-check"></i><b>14.2.1</b> Merge Conflicts</a></li>
</ul></li>
<li class="chapter" data-level="14.3" data-path="git-branches.html"><a href="git-branches.html#undoing-changes"><i class="fa fa-check"></i><b>14.3</b> Undoing Changes</a></li>
<li class="chapter" data-level="14.4" data-path="git-branches.html"><a href="git-branches.html#github-and-branches"><i class="fa fa-check"></i><b>14.4</b> GitHub and Branches</a><ul>
<li class="chapter" data-level="14.4.1" data-path="git-branches.html"><a href="git-branches.html#github-pages"><i class="fa fa-check"></i><b>14.4.1</b> GitHub Pages</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="git-branches.html"><a href="git-branches.html#resources-13"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="15" data-path="git-collaboration.html"><a href="git-collaboration.html"><i class="fa fa-check"></i><b>15</b> Git Collaboration</a><ul>
<li class="chapter" data-level="15.1" data-path="git-collaboration.html"><a href="git-collaboration.html#centralized-workflow"><i class="fa fa-check"></i><b>15.1</b> Centralized Workflow</a></li>
<li class="chapter" data-level="15.2" data-path="git-collaboration.html"><a href="git-collaboration.html#feature-branch-workflow"><i class="fa fa-check"></i><b>15.2</b> Feature Branch Workflow</a></li>
<li class="chapter" data-level="15.3" data-path="git-collaboration.html"><a href="git-collaboration.html#forking-workflow"><i class="fa fa-check"></i><b>15.3</b> Forking Workflow</a><ul>
<li class="chapter" data-level="15.3.1" data-path="git-collaboration.html"><a href="git-collaboration.html#pull-requests"><i class="fa fa-check"></i><b>15.3.1</b> Pull Requests</a></li>
</ul></li>
<li class="chapter" data-level="" data-path="git-collaboration.html"><a href="git-collaboration.html#resources-14"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="16" data-path="shiny.html"><a href="shiny.html"><i class="fa fa-check"></i><b>16</b> The <code>shiny</code> Framework</a><ul>
<li class="chapter" data-level="16.1" data-path="shiny.html"><a href="shiny.html#creating-shiny-apps"><i class="fa fa-check"></i><b>16.1</b> Creating Shiny Apps</a><ul>
<li class="chapter" data-level="16.1.1" data-path="shiny.html"><a href="shiny.html#application-structure"><i class="fa fa-check"></i><b>16.1.1</b> Application Structure</a></li>
<li class="chapter" data-level="16.1.2" data-path="shiny.html"><a href="shiny.html#the-ui"><i class="fa fa-check"></i><b>16.1.2</b> The UI</a></li>
<li class="chapter" data-level="16.1.3" data-path="shiny.html"><a href="shiny.html#the-server"><i class="fa fa-check"></i><b>16.1.3</b> The Server</a></li>
</ul></li>
<li class="chapter" data-level="16.2" data-path="shiny.html"><a href="shiny.html#publishing-shiny-apps"><i class="fa fa-check"></i><b>16.2</b> Publishing Shiny Apps</a></li>
<li class="chapter" data-level="" data-path="shiny.html"><a href="shiny.html#resources-15"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="appendix"><span><b>Special Topics</b></span></li>
<li class="chapter" data-level="A" data-path="plotly.html"><a href="plotly.html"><i class="fa fa-check"></i><b>A</b> Plotly</a><ul>
<li class="chapter" data-level="A.1" data-path="plotly.html"><a href="plotly.html#getting-started"><i class="fa fa-check"></i><b>A.1</b> Getting Started</a></li>
<li class="chapter" data-level="A.2" data-path="plotly.html"><a href="plotly.html#basic-charts"><i class="fa fa-check"></i><b>A.2</b> Basic Charts</a></li>
<li class="chapter" data-level="A.3" data-path="plotly.html"><a href="plotly.html#layout"><i class="fa fa-check"></i><b>A.3</b> Layout</a></li>
<li class="chapter" data-level="A.4" data-path="plotly.html"><a href="plotly.html#hovers"><i class="fa fa-check"></i><b>A.4</b> Hovers</a></li>
<li class="chapter" data-level="" data-path="plotly.html"><a href="plotly.html#resources-16"><i class="fa fa-check"></i>Resources</a></li>
</ul></li>
<li class="chapter" data-level="B" data-path="control-structures.html"><a href="control-structures.html"><i class="fa fa-check"></i><b>B</b> R Language Control Structures</a><ul>
<li class="chapter" data-level="B.1" data-path="control-structures.html"><a href="control-structures.html#loops"><i class="fa fa-check"></i><b>B.1</b> Loops</a><ul>
<li class="chapter" data-level="B.1.1" data-path="control-structures.html"><a href="control-structures.html#for-loop"><i class="fa fa-check"></i><b>B.1.1</b> For Loop</a></li>
<li class="chapter" data-level="B.1.2" data-path="control-structures.html"><a href="control-structures.html#while-loop"><i class="fa fa-check"></i><b>B.1.2</b> While-loop</a></li>
<li class="chapter" data-level="B.1.3" data-path="control-structures.html"><a href="control-structures.html#repeat-loop"><i class="fa fa-check"></i><b>B.1.3</b> repeat-loop</a></li>
<li class="chapter" data-level="B.1.4" data-path="control-structures.html"><a href="control-structures.html#leaving-early-break-and-next"><i class="fa fa-check"></i><b>B.1.4</b> Leaving Early: <code>break</code> and <code>next</code></a></li>
<li class="chapter" data-level="B.1.5" data-path="control-structures.html"><a href="control-structures.html#when-not-to-use-loops-in-r"><i class="fa fa-check"></i><b>B.1.5</b> When (Not) To Use Loops In R?</a></li>
</ul></li>
<li class="chapter" data-level="B.2" data-path="control-structures.html"><a href="control-structures.html#more-about-if-and-else"><i class="fa fa-check"></i><b>B.2</b> More about <code>if</code> and <code>else</code></a><ul>
<li class="chapter" data-level="B.2.1" data-path="control-structures.html"><a href="control-structures.html#where-to-put-else"><i class="fa fa-check"></i><b>B.2.1</b> Where To Put Else</a></li>
<li class="chapter" data-level="B.2.2" data-path="control-structures.html"><a href="control-structures.html#return-value"><i class="fa fa-check"></i><b>B.2.2</b> Return Value</a></li>
</ul></li>
<li class="chapter" data-level="B.3" data-path="control-structures.html"><a href="control-structures.html#switch-choosing-between-multiple-conditions"><i class="fa fa-check"></i><b>B.3</b> <code>switch</code>: Choosing Between Multiple Conditions</a></li>
</ul></li>
<li class="chapter" data-level="C" data-path="data-tables.html"><a href="data-tables.html"><i class="fa fa-check"></i><b>C</b> Thinking Big: Data Tables</a><ul>
<li class="chapter" data-level="C.1" data-path="data-tables.html"><a href="data-tables.html#background-passing-by-value-and-passing-by-reference"><i class="fa fa-check"></i><b>C.1</b> Background: Passing By Value And Passing By Reference</a></li>
<li class="chapter" data-level="C.2" data-path="data-tables.html"><a href="data-tables.html#data-tables-introduction"><i class="fa fa-check"></i><b>C.2</b> Data Tables: Introduction</a><ul>
<li class="chapter" data-level="C.2.1" data-path="data-tables.html"><a href="data-tables.html#replacement-for-data-frames-sort-of"><i class="fa fa-check"></i><b>C.2.1</b> Replacement for Data Frames (Sort of)</a></li>
<li class="chapter" data-level="C.2.2" data-path="data-tables.html"><a href="data-tables.html#fast-reading-and-writing"><i class="fa fa-check"></i><b>C.2.2</b> Fast Reading and Writing</a></li>
</ul></li>
<li class="chapter" data-level="C.3" data-path="data-tables.html"><a href="data-tables.html#indexing-the-major-powerhorse-of-data-tables"><i class="fa fa-check"></i><b>C.3</b> Indexing: The Major Powerhorse of Data Tables</a><ul>
<li class="chapter" data-level="C.3.1" data-path="data-tables.html"><a href="data-tables.html#i-select-observations"><i class="fa fa-check"></i><b>C.3.1</b> i: Select Observations</a></li>
<li class="chapter" data-level="C.3.2" data-path="data-tables.html"><a href="data-tables.html#j-work-with-columns"><i class="fa fa-check"></i><b>C.3.2</b> j: Work with Columns</a></li>
<li class="chapter" data-level="C.3.3" data-path="data-tables.html"><a href="data-tables.html#group-in-by"><i class="fa fa-check"></i><b>C.3.3</b> Group in <code>by</code></a></li>
</ul></li>
<li class="chapter" data-level="C.4" data-path="data-tables.html"><a href="data-tables.html#create-variables-by-reference"><i class="fa fa-check"></i><b>C.4</b> <code>:=</code>–Create variables by reference</a></li>
<li class="chapter" data-level="C.5" data-path="data-tables.html"><a href="data-tables.html#keys"><i class="fa fa-check"></i><b>C.5</b> keys</a></li>
<li class="chapter" data-level="C.6" data-path="data-tables.html"><a href="data-tables.html#resources-17"><i class="fa fa-check"></i><b>C.6</b> Resources</a></li>
</ul></li>
<li class="chapter" data-level="D" data-path="remote-server.html"><a href="remote-server.html"><i class="fa fa-check"></i><b>D</b> Using Remote Server</a><ul>
<li class="chapter" data-level="D.1" data-path="remote-server.html"><a href="remote-server.html#server-setup"><i class="fa fa-check"></i><b>D.1</b> Server Setup</a></li>
<li class="chapter" data-level="D.2" data-path="remote-server.html"><a href="remote-server.html#connecting-to-the-remote-server"><i class="fa fa-check"></i><b>D.2</b> Connecting to the Remote Server</a></li>
<li class="chapter" data-level="D.3" data-path="remote-server.html"><a href="remote-server.html#copying-files"><i class="fa fa-check"></i><b>D.3</b> Copying Files</a><ul>
<li class="chapter" data-level="D.3.1" data-path="remote-server.html"><a href="remote-server.html#scp"><i class="fa fa-check"></i><b>D.3.1</b> scp</a></li>
<li class="chapter" data-level="D.3.2" data-path="remote-server.html"><a href="remote-server.html#rsync"><i class="fa fa-check"></i><b>D.3.2</b> rsync</a></li>
<li class="chapter" data-level="D.3.3" data-path="remote-server.html"><a href="remote-server.html#graphical-frontends"><i class="fa fa-check"></i><b>D.3.3</b> Graphical Frontends</a></li>
<li class="chapter" data-level="D.3.4" data-path="remote-server.html"><a href="remote-server.html#remote-editing"><i class="fa fa-check"></i><b>D.3.4</b> Remote Editing</a></li>
</ul></li>
<li class="chapter" data-level="D.4" data-path="remote-server.html"><a href="remote-server.html#r-and-rscript"><i class="fa fa-check"></i><b>D.4</b> R and Rscript</a><ul>
<li class="chapter" data-level="D.4.1" data-path="remote-server.html"><a href="remote-server.html#graphics-output-with-no-gui"><i class="fa fa-check"></i><b>D.4.1</b> Graphics Output with No GUI</a></li>
</ul></li>
<li class="chapter" data-level="D.5" data-path="remote-server.html"><a href="remote-server.html#life-on-server"><i class="fa fa-check"></i><b>D.5</b> Life on Server</a><ul>
<li class="chapter" data-level="D.5.1" data-path="remote-server.html"><a href="remote-server.html#be-social"><i class="fa fa-check"></i><b>D.5.1</b> Be Social!</a></li>
<li class="chapter" data-level="D.5.2" data-path="remote-server.html"><a href="remote-server.html#useful-things-to-do"><i class="fa fa-check"></i><b>D.5.2</b> Useful Things to Do</a></li>
<li class="chapter" data-level="D.5.3" data-path="remote-server.html"><a href="remote-server.html#permissions-and-ownership"><i class="fa fa-check"></i><b>D.5.3</b> Permissions and ownership</a></li>
<li class="chapter" data-level="D.5.4" data-path="remote-server.html"><a href="remote-server.html#more-than-one-connection"><i class="fa fa-check"></i><b>D.5.4</b> More than One Connection</a></li>
</ul></li>
<li class="chapter" data-level="D.6" data-path="remote-server.html"><a href="remote-server.html#advanced-usage"><i class="fa fa-check"></i><b>D.6</b> Advanced Usage</a><ul>
<li class="chapter" data-level="D.6.1" data-path="remote-server.html"><a href="remote-server.html#ssh-keys-.sshconfig"><i class="fa fa-check"></i><b>D.6.1</b> ssh keys, .ssh/config</a></li>
<li class="chapter" data-level="D.6.2" data-path="remote-server.html"><a href="remote-server.html#more-about-command-line-pipes-and-shell-patterns"><i class="fa fa-check"></i><b>D.6.2</b> More about command line: pipes and shell patterns</a></li>
<li class="chapter" data-level="D.6.3" data-path="remote-server.html"><a href="remote-server.html#running-rscript-in-ssh-session"><i class="fa fa-check"></i><b>D.6.3</b> Running RScript in ssh Session</a></li>
</ul></li>
</ul></li>
<li class="divider"></li>
<li><a href="https://github.com/rstudio/bookdown" target="blank">Published with bookdown</a></li>

</ul>

      </nav>
    </div>

    <div class="book-body">
      <div class="body-inner">
        <div class="book-header" role="navigation">
          <h1>
            <i class="fa fa-circle-o-notch fa-spin"></i><a href="./">Technical Foundations of Informatics</a>
          </h1>
        </div>

        <div class="page-wrapper" tabindex="-1" role="main">
          <div class="page-inner">

            <section class="normal" id="section-">
<div id="r-intro" class="section level1">
<h1><span class="header-section-number">Chapter 5</span> Introduction to R</h1>
<p>R is an extraordinarily powerful open-source software program built for working with data. It is one of the most popular data science tools because of its ability to efficiently perform statistical analysis, implement machine learning algorithms, and create data visualizations. R is the primary programming language used throughout this book, and understanding its foundational operations is key to being able to perform more complex tasks.</p>
<div id="programming-with-r" class="section level2">
<h2><span class="header-section-number">5.1</span> Programming with R</h2>
<p>R is a <strong>statistical programming language</strong> that allows you to write code to work with data. It is an <strong>open-source</strong> programming language, which means that it is free and continually improved upon by the R community. The R language has a number of functionalities that allow you to read, analyze, and visualize datasets.</p>
<ul>
<li><em>Fun Fact:</em> R is called “R” because it was inspired by and comes after the language “S”, a language for <strong>S</strong>tatistics developed by AT&amp;T.</li>
</ul>
<p>So far you’ve leveraged formal language to give instructions to your computers, such as by writing syntactically-precise instructions at the command-line. Programming in R will work in a similar manner: you will write instructions using R’s special language and syntax, which the computer will <strong>interpret</strong> as instructions for how to work with data.</p>
<p>However, as projects grow in complexity, it will become useful if you can write down all the instructions in a single place, and then order the computer to <em>execute</em> all of those instructions at once. This list of instructions is called a <strong>script</strong>. Executing or “running” a script will cause each instruction (line of code) to be run <em>in order, one after the other</em>, just as if you had typed them in one by one. Writing scripts allows you to save, share, and re-use your work. By saving instructions in a file (or set of files), you can easily check, change, and re-execute the list of instructions as you figure out how to use data to answer questions. And, because R is an <em>interpreted</em> language rather than a <em>compiled</em> language like Java, R programming environments will also give you the ability to execute each individual line of code in your script if you desire (though this will become cumbersome as projects become large).</p>
<p>As you begin working with data in R, you will be writing multiple instructions (lines of code) and saving them in files with the <strong><code>.R</code></strong> extension, representing R scripts. You can write this R code in any text editor (such as Atom), but we recommend you usually use a program called <strong>RStudio</strong> which is specialized for writing and running R scripts.</p>
</div>
<div id="running-r-scripts" class="section level2">
<h2><span class="header-section-number">5.2</span> Running R Scripts</h2>
<p>R scripts (programs) are just a sequence of instructions, and there are a couple of different ways in which we can tell the computer to execute these instructions.</p>
<div id="running-r-cmd" class="section level3">
<h3><span class="header-section-number">5.2.1</span> Command-Line</h3>
<p>It is possible to issue R instructions (run lines of code) one-by-one at the command-line by starting an <strong>interactive R session</strong> within your terminal. This will allow you to type R code directly into the terminal, and your computer will interpret and execute each line of code (if you just typed R syntax directly into the terminal, your computer wouldn’t understand it).</p>
<p>With R installed, you can start an interactive R session on a Mac by typing <code>R</code> into the terminal (to run the <code>R</code> program), or on Windows by running the “R” desktop app program. This will start the session and provide you with lots of information about the R language:</p>
<div class="figure">
<img src="img/r-intro/r-interactive-session.png" title="interactive R session" alt="An interactive R session running in the terminal." />
<p class="caption">An interactive R session running in the terminal.</p>
</div>
<p>Notice that this description also include <em>instructions on what to do next</em>—most importantly <code>&quot;Type 'q()' to quit R.&quot;</code>.</p>
<p class="alert alert-warning">
Always read the output when working on the command-line!
</p>
<p>Once you’ve started running an interactive R session, you can begin entering one line of code at a time at the prompt (<code>&gt;</code>). This is a nice way to experiment with the R language or to quickly run some code. For example, try doing some math at the command prompt (i.e., enter <code>1 + 1</code> and see the output).</p>
<ul>
<li>Note that RStudio also provides an interactive console that provides the exact same functionality.</li>
</ul>
<p>It is also possible to run entire scripts from the command-line by using the <code>RScript</code> program, specifying the <code>.R</code> file you wish to execute:</p>
<div class="figure">
<img src="img/r-intro/rscript-terminal.png" title="RScript from the terminal" alt="Using RScript from the terminal" />
<p class="caption">Using RScript from the terminal</p>
</div>
<p>Entering this command in the terminal would execute each line of R code written in the <code>analysis.R</code> file, performing all of the instructions that you had save there. This is helpful if your data has changed, and you want to reproduce the results of your analysis using the same instructions.</p>
<div id="windows-command-line" class="section level4">
<h4><span class="header-section-number">5.2.1.1</span> Windows Command-Line</h4>
<p>On Windows, you need to tell the computer where to find the <code>R.exe</code> and <code>RScript.exe</code> programs to execute—that is, what is the <strong>path</strong> to these programs. You can do this by specifying the <em>absolute path</em> to the R program when you execute it, for example:</p>
<div class="figure">
<img src="img/r-intro/rscript-terminal-windows.png" title="Rscript from windows shell" alt="Using RScript from a Windows shell" />
<p class="caption">Using RScript from a Windows shell</p>
</div>
<p>If you plan to run R from the command-line regularly (<em>not</em> a requirement for this course), a better solution is to add the folder containing these programs to your computer’s <a href="https://en.wikipedia.org/wiki/PATH_(variable)"><strong><code>PATH</code> variable</strong></a>. This is a <em>system-level</em> variable that contains a list of folders that the computer searches when finding programs to execute execute. The reason the computer knows where to find the <code>git.exe</code> program when you type <code>git</code> in the command-line is because that program is “on the <code>PATH</code>”.</p>
<p>In Windows, You can add the <code>R.exe</code> and <code>RScript.exe</code> programs to your computer’s <code>PATH</code> by editing your machine’s <strong>Environment Variables</strong> through the <em>Control Panel</em>:</p>
<ul>
<li><p>Open up the “Advanced” tab of the “System Properties”. In Windows 10, you can find this by searching for “environment”. Click on the “Environment Variables…” button to open the settings for the Environment Variables.</p></li>
<li><p>In the window that pops up, select the “PATH” variable (either per user or for the whole system) and click the “Edit” button below it.</p></li>
<li><p>In the next window that pops up, click the “Browse” button to select the <em>folder that contains</em> the <code>R.exe</code> and <code>RScript.exe</code> files. See the above screenshot for one possible path.</p></li>
<li><p>You will need to close and re-open your command-line (Git Bash) for the <code>PATH</code> changes to take effect.</p></li>
</ul>
<p>Overall, using R from the command-line can be tricky; we recommend you just use RStudio instead.</p>
</div>
</div>
<div id="running-r-rstudio" class="section level3">
<h3><span class="header-section-number">5.2.2</span> RStudio</h3>
<p>RStudio is an open-source <strong>integrated development environment (IDE)</strong> that provides an informative user interface for interacting with the R interpreter. IDEs provide a platform for writing <em>and</em> executing code, including viewing the results of the code you have run. If you haven’t already, make sure to download and install <a href="https://www.rstudio.com/products/rstudio/download3/#download">the free version of RStudio</a>.</p>
<p>When you open the RStudio program (either by searching for it, or double-clicking on a desktop icon), you’ll see the following interface:</p>
<div class="figure">
<img src="img/r-intro/rstudio-interface.png" title="Rstudio&#39;s user interface" alt="RStudio’s user interface. Annotations are in red." />
<p class="caption">RStudio’s user interface. Annotations are in red.</p>
</div>
<p>An RStudio session usually involves 4 sections (“panes”), though you can customize this layout if you wish:</p>
<ul>
<li><p><strong>Script</strong>: The top-left pane is a simple text editor for writing your R code. While it is not as robust as a text editing program like Atom, it will colorize code, “auto-complete” text, and allows you to easily execute your code. Note that this pane is hidden if there are no open scripts; select <code>File &gt; New File &gt; R Script</code> from the menu to create a new script file.</p>
<p>In order to execute (run) the code you write, you have two options:</p>
<ol style="list-style-type: decimal">
<li><p>You can execute a section of your script by selecting (highlighting) the desired code and pressing the “Run” button (keyboard shortcut: <code>ctrl</code> and <code>enter</code>). If no lines are selected, this will run the line currently containing the cursor. This is the most common way to execute code in R.</p>
<ul>
<li><em>Protip:</em> use <code>cmd + a</code> to select the entire script!</li>
</ul></li>
<li><p>You can execute an entire script by using the <code>Source</code> command to treat the current file as the “source” of code. Press the “Source” button (hover the mouse over it for keyboard shortcuts) to do so. If you check the “Source on save” option, your entire script will be executed every time you save the file (this may or may not be appropriate, depending on the complexity of your script and its output).</p></li>
</ol></li>
<li><p><strong>Console</strong>: The bottom-left pane is a console for entering R commands. This is identical to an inetractive session you’d run on the command-line, in which you can type and execute one line of code at a time. The console will also show the printed results from executing the code you execute from the Script pane.</p>
<ul>
<li><em>Protip:</em> just like with the command-line, you can <strong>use the up arrow</strong> to easily access previously executed lines of code.</li>
</ul></li>
<li><p><strong>Environment</strong>: The top-right pane displays information about the current R environment—specifically, information that you have stored inside of <em>variables</em> (see below). In the above example, the value <code>201</code> is stored in a variable called <code>x</code>. You’ll often create dozens of variables within a script, and the Environment pane helps you keep track of which values you have stored in what variables. <em>This is incredibly useful for debugging!</em></p></li>
<li><p><strong>Plots, packages, help, etc.</strong>: The bottom right pane contains multiple tabs for accessing various information about your program. When you create visualizations, those plots will render in this quadrant. You can also see what packages you’ve loaded or look up information about files. <em>Most importantly</em>, this is also where you can access the official documentation for the R language. If you ever have a question about how something in R works, this is a good place to start!</p></li>
</ul>
<p>Note, you can use the small spaces between the quadrants to adjust the size of each area to your liking. You can also use menu options to reorganize the panes if you wish.</p>
</div>
</div>
<div id="comments" class="section level2">
<h2><span class="header-section-number">5.3</span> Comments</h2>
<p>Before discussing how to program with R, we need to talk about a piece of syntax that lets you comment your code. In programming, <strong>comments</strong> are bits of text that are <em>not interpreted as computer instructions</em>—they aren’t code, they’re just notes about the code! Since computer code can be opaque and difficult to understand, we use comments to help write down the meaning and <em>purpose</em> of our code. While a computer is able to understand the code, comments are there to help <em>people</em> understand it. This is particularly imporant when someone else will be looking at your work—whether that person is a collaborator, or is simply a future version of you (e.g., when you need to come back and fix something and so need to remember what you were even thinking).</p>
<p>Comments should be clear, concise, and helpful—they should provide information that is not otherwise present or “obvious” in the code itself.</p>
<p>In R, we mark text as a comment by putting it after the pound/hashtag symbol (<strong><code>#</code></strong>). Everything from the <code>#</code> until the end of the line is a comment. We put descriptive comments <em>immediately above</em> the code it describes, but you can also put very short notes at the end of the line of code (preferably following two spaces):</p>
<div class="sourceCode" id="cb26"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb26-1" data-line-number="1"><span class="co"># Set how many bottles of beer are on the wall</span></a>
<a class="sourceLine" id="cb26-2" data-line-number="2">bottles &lt;-<span class="st"> </span><span class="dv">99</span> <span class="op">-</span><span class="st"> </span><span class="dv">1</span>  <span class="co"># 98 bottles</span></a></code></pre></div>
<p>(You may recognize this <code>#</code> syntax and commenting behavior from the command-line and git chapters. That’s because the same syntax is used in a Bash shell!)</p>
</div>
<div id="variables" class="section level2">
<h2><span class="header-section-number">5.4</span> Variables</h2>
<p>Since computer programs involve working with lots of <em>information</em>, we
need a way to store and refer to this information. We do this with
<strong>variables</strong>. Variables are labels for information stored in memory; in R, you can think of them as “boxes” or “nametags” for data. After putting data in a variable box, you can then refer to that data by the name on the box.</p>
<p>Variable names can contain any combination of letters, numbers, periods (<code>.</code>), or underscores (<code>_</code>). Variables names must begin with a letter. Note that like everything in programming, variable names are case sensitive. It is best practice to make variable names descriptive and information about what data they contain. <code>a</code> is not a good variable name. <code>cups_of_coffee</code> is a good variable name. In this course, we will use the <a href="http://style.tidyverse.org/">Tidyverse Style Guide</a> as a foundation of <em>how we should style our code</em>. To comply with this style guide, variables should be <strong>all lower-case letters, separated by underscore (<code>_</code>)</strong>. This is also known as <strong>snake_case</strong>.</p>
<p class="alert alert-info">
<strong>Note:</strong> There is an important distinction between <em>syntax</em> and <em>style</em>. You need to use the proper <em>syntax</em> such that your <em>machine</em> understands your code. This requires that you follow a set of rigid rules for what code can be procesed. <em>Style</em> is what helps make your code understandable for other <em>humans</em>. Good style is not required to get your code to run, but it’s imperative for writing clear, (human) readable code.
</p>
<p>We call putting information in a variable <strong>assigning</strong> that value to the variable. We do this using the <em>assignment operator</em> <strong><code>&lt;-</code></strong>. For example:</p>
<div class="sourceCode" id="cb27"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb27-1" data-line-number="1"><span class="co"># Stores the number 7 into a variable called `shoe_size`</span></a>
<a class="sourceLine" id="cb27-2" data-line-number="2">shoe_size &lt;-<span class="st"> </span><span class="dv">7</span></a></code></pre></div>
<ul>
<li><em>Notice:</em> variable name goes on the left, value goes on the right!</li>
</ul>
<p>You can see what value (data) is inside a variable by either typing that variable name as a line of code, or by using R’s built-in <code>print()</code> function (more on functions later):</p>
<div class="sourceCode" id="cb28"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb28-1" data-line-number="1"><span class="kw">print</span>(shoe_size)</a>
<a class="sourceLine" id="cb28-2" data-line-number="2"><span class="co"># [1] 7</span></a></code></pre></div>
<ul>
<li>We’ll talk about the <code>[1]</code> in that output later.</li>
</ul>
<p>You can also use <strong>mathematical operators</strong> (e.g., <code>+</code>, <code>-</code>, <code>/</code>, <code>*</code>) when assigning values to variables. For example, you could create a variable that is the sum of two numbers as follows:</p>
<div class="sourceCode" id="cb29"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb29-1" data-line-number="1">x &lt;-<span class="st"> </span><span class="dv">3</span> <span class="op">+</span><span class="st"> </span><span class="dv">4</span></a></code></pre></div>
<p>Once a value (like a number) is <em>in</em> a variable, you can use that variable in place of any other value. So all of the following are valid:</p>
<div class="sourceCode" id="cb30"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb30-1" data-line-number="1">x &lt;-<span class="st"> </span><span class="dv">2</span>  <span class="co"># store 2 in x</span></a>
<a class="sourceLine" id="cb30-2" data-line-number="2">y &lt;-<span class="st"> </span><span class="dv">9</span>  <span class="co"># store 9 in y</span></a>
<a class="sourceLine" id="cb30-3" data-line-number="3">z &lt;-<span class="st"> </span>x <span class="op">+</span><span class="st"> </span>y  <span class="co"># store sum of x and y in z</span></a>
<a class="sourceLine" id="cb30-4" data-line-number="4"><span class="kw">print</span>(z)  <span class="co"># 11</span></a>
<a class="sourceLine" id="cb30-5" data-line-number="5">z &lt;-<span class="st"> </span>z <span class="op">+</span><span class="st"> </span><span class="dv">1</span>  <span class="co"># take z, add 1, and store result back in z</span></a>
<a class="sourceLine" id="cb30-6" data-line-number="6"><span class="kw">print</span>(z)  <span class="co"># 12</span></a></code></pre></div>
<div id="basic-data-types" class="section level3">
<h3><span class="header-section-number">5.4.1</span> Basic Data Types</h3>
<p>In the example above, we stored <strong>numeric</strong> values in variables. R is a <strong>dynamically typed language</strong>, which means that we <em>do not</em> need to explicitly state what type of information will be stored in each variable we create. R is intelligent enough to understand that if we have code <code>x &lt;- 7</code>, then <code>x</code> will contain a numeric value (and so we can do math upon it!)</p>
<p>There six “basic types” (called <em>atomic data types</em>) for data in R:</p>
<ul>
<li><p><strong>Numeric</strong>: The default computational data type in R is numeric data, which consists of the set of real numbers (including decimals). We use use <strong>mathematical operators</strong> on numeric data (such as <code>+</code>, <code>-</code>, <code>*</code>, <code>-</code>, etc.). There are also numerous functions that work on numeric data (such as calculating sums or averages).</p></li>
<li><p><strong>Character</strong>: Character data stores <em>strings</em> of characters (things you type with a keyboard) in a variable. You specify that some information is character data by surrounding it in either single quotes (<strong><code>'</code></strong>) or double quotes (<strong><code>&quot;</code></strong>). To comply with the <a href="http://style.tidyverse.org/syntax.html#quotes">style guide</a>, we’ll consider it best practice to use <strong>double quotes</strong>.</p>
<div class="sourceCode" id="cb31"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb31-1" data-line-number="1"><span class="co"># Create character variable `famous.poet` with the value &quot;Bill Shakespeare&quot;</span></a>
<a class="sourceLine" id="cb31-2" data-line-number="2">famous_poet &lt;-<span class="st"> &quot;Bill Shakespeare&quot;</span></a></code></pre></div>
<p>Note that character data <em>is still data</em>, so it can be assigned to a variable just like numeric data!</p>
<p>There are no special operators for character data, though there are a many built-in functions for working with strings.</p></li>
<li><p><strong>Logical</strong>: Logical (a.k.a Boolean) data types store “yes-or-no”
data. A logical value can be one of two values: <code>TRUE</code> or
<code>FALSE</code>. Importantly, these <strong>are not</strong> the strings <code>&quot;TRUE&quot;</code> or
<code>&quot;FALSE&quot;</code>; logical values are a different type! In interactive
session, you can use the shorthand <code>T</code> or <code>F</code> in lieu of <code>TRUE</code> and
<code>FALSE</code> in variable assignment but this is not recommended for
programs.</p>
<ul>
<li><em>Fun fact:</em> logical values are called “booleans” after mathematician and logician <a href="https://en.wikipedia.org/wiki/George_Boole">George Boole</a>.</li>
</ul>
<p>Logical values are most commonly the result of applying a <strong>relational operator</strong> (also called a <strong>comparison operator</strong>) to some other data. Comparison operators are used to compare values and include: <code>&lt;</code> (less than), <code>&gt;</code> (greater than), <code>&lt;=</code> (less-than-or-equal), <code>&gt;=</code> (greater-than-or-equal), <code>==</code> (equal), and <code>!=</code> (not-equal).</p>
<div class="sourceCode" id="cb32"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb32-1" data-line-number="1"><span class="co"># Store values in variables</span></a>
<a class="sourceLine" id="cb32-2" data-line-number="2">x &lt;-<span class="st"> </span><span class="dv">3</span></a>
<a class="sourceLine" id="cb32-3" data-line-number="3">y &lt;-<span class="st"> </span><span class="fl">3.15</span></a>
<a class="sourceLine" id="cb32-4" data-line-number="4"></a>
<a class="sourceLine" id="cb32-5" data-line-number="5"><span class="co"># Compare values in x and y</span></a>
<a class="sourceLine" id="cb32-6" data-line-number="6">x <span class="op">&gt;</span><span class="st"> </span>y  <span class="co"># returns logical value FALSE (x IS NOT bigger than y)</span></a>
<a class="sourceLine" id="cb32-7" data-line-number="7">y <span class="op">!=</span><span class="st"> </span>x  <span class="co"># returns logical value TRUE (y IS not-equal to x)</span></a>
<a class="sourceLine" id="cb32-8" data-line-number="8"></a>
<a class="sourceLine" id="cb32-9" data-line-number="9"><span class="co"># compare x to pi (built-in variable)</span></a>
<a class="sourceLine" id="cb32-10" data-line-number="10">y <span class="op">==</span><span class="st"> </span>pi  <span class="co"># returns logical value FALSE</span></a>
<a class="sourceLine" id="cb32-11" data-line-number="11"></a>
<a class="sourceLine" id="cb32-12" data-line-number="12"><span class="co"># compare strings (based on alphabetical ordering)</span></a>
<a class="sourceLine" id="cb32-13" data-line-number="13"><span class="st">&quot;cat&quot;</span> <span class="op">&gt;</span><span class="st"> &quot;dog&quot;</span>  <span class="co"># returns FALSE</span></a></code></pre></div>
<p>Logical values have their own operators as well (called <strong>logical operators</strong> or <strong>boolean operators</strong>). These <em>apply to</em> logical values and <em>produce</em> logical values, allowing you to make more complex logical expressions. These include <code>&amp;</code> (and), <code>|</code> (or), and <code>!</code> (not).</p>
<div class="sourceCode" id="cb33"><pre class="sourceCode r"><code class="sourceCode r"><a class="sourceLine" id="cb33-1" data-line-number="1"><span class="co"># Store values in variables</span></a>
<a class="sourceLine" id="cb33-2" data-line-number="2">x &lt;-<span class="st"> </span><span class="fl">3.1</span></a>
<a class="sourceLine" id="cb33-3" data-line-number="3">y &lt;-<span class="st"> </span><span class="fl">3.2</span></a>
<a class="sourceLine" id="cb33-4" data-line-number="4">pet &lt;-<span class="st"> &quot;dog&quot;</span></a>
<a class="sourceLine" id="cb33-5" data-line-number="5">weather &lt;-<span class="st"> &quot;rain&quot;</span></a>
<a class="sourceLine" id="cb33-6" data-line-number="6"></a>
<a class="sourceLine" id="cb33-7" data-line-number="7"><span class="co"># Check if x is less than pi AND y is greater than pi</span></a>
<a class="sourceLine" id="cb33-8" data-line-number="8">x <span class="op">&lt;</span><span class="st"> </span>pi <span class="op">&amp;</span><span class="st"> </span>y <span class="op">&gt;</span><span class="st"> </span>pi  <span class="co"># TRUE</span></a>
<a class="sourceLine" id="cb33-9" data-line-number="9"></a>
<a class="sourceLine" id="cb33-10" data-line-number="10"><span class="co"># Check if pet is &quot;cat&quot; OR &quot;dog&quot;</span></a>
<a class="sourceLine" id="cb33-11" data-line-number="11">pet <span class="op">==</span><span class="st"> &quot;cat&quot;</span> <span class="op">|</span><span class="st"> </span>pet <span class="op">==</span><span class="st"> &quot;dog&quot;</span>  <span class="co"># TRUE</span></a>
<a class="sourceLine" id="cb33-12" data-line-number="12"></a>
<a class="sourceLine" id="cb33-13" data-line-number="13"><span class="co"># Check if pet is &quot;dog&quot; AND NOT weather is &quot;rain&quot;</span></a>
<a class="sourceLine" id="cb33-14" data-line-number="14">pet <span class="op">==</span><span class="st"> &quot;dog&quot;</span> <span class="op">&amp;</span><span class="st"> </span><span class="op">!</span>(weather <span class="op">==</span><span class="st"> &quot;rain&quot;</span>)  <span class="co"># FALSE</span></a></code></pre></div>
<p>Note that it’s easy to write complex expressions with logical operators. If you find yourself getting lost, I recommend rethinking your question to see if there is a simpler way to express it!</p></li>
<li><p><strong>Integer</strong>: Integer values are technically a different data type than numeric values because of how they are stored and manipulated by the R interpreter. This is something that you will rarely encounter, but it’s good to know that you can specify a number is of integer type rather than general numeric type by placing a capital <code>L</code> (for “long integer”) after an value in variable assignment (<code>my_integer &lt;- 10L</code>).</p></li>
<li><p><strong>Complex</strong>: Complex (imaginary) numbers have their own data storage
type in R, are are created using the <code>i</code> syntax: <code>complex_variable   &lt;- 1 + 2i</code>. We will not be using complex numbers in this course.</p></li>
<li><p><strong>Raw</strong>: is a sequence of “raw” data. It is good for storing a “raw”
sequence of bytes, such as image data. R does not interpret raw data
in any particular way. We will not discuss raw data in this book.</p></li>
</ul>
</div>
</div>
<div id="gettinghelp" class="section level2">
<h2><span class="header-section-number">5.5</span> Getting Help</h2>
<p>As with any programming language, when working in R you will inevitably run into problems, confusing situations, or just general questions. Here are a few ways to start getting help.</p>
<ol style="list-style-type: decimal">
<li><p><strong>Read the error messages</strong>: If there is an issue with the way you
have written or executed your code, R will often print out a red error message in your console. Do you best to decipher the message (read it carefully, and think about what is meant by each word in the message), or you can put it directly into Google to get more information. You’ll soon get the hang of interpreting these messages if you put the time into trying to understand them.</p></li>
<li><p><strong>Google</strong>: When you’re trying to figure out how to do something, it should be no surprise that Google is often the best resource. Try searching for queries like <code>&quot;how to &lt;DO THING&gt; in R&quot;</code>. More frequently than not, your question will lead you to a Q/A forum called StackOverflow (see below), which is a great place to find potential answers.</p></li>
<li><p><strong>StackOverflow</strong>: StackOverflow is an amazing Q/A forum for asking/answering programming questions. Indeed, most basic questions have already been asked/answered here. However, don’t hesitate to post your own questions to StackOverflow. Be sure to hone in on the specific question you’re trying to answer, and provide error messages and sample code. I often find that, by the time I can articulate the question clearly enough to post it, I’ve figured out my problem anyway.</p>
<ul>
<li>There is a classical method of debugging called <a href="https://en.wikipedia.org/wiki/Rubber_duck_debugging">rubber duck debugging</a>, which involves simply trying to explain your code/problem to an inanimate object (talking to pets works too). You’ll usually be able to fix the problem if you just step back and think about how you would explain it to someone else!</li>
</ul></li>
<li><p><strong>Documentation</strong>: R’s documentation is actually quite good. Functions and behaviors are all described in the same format, and often contain helpful examples. To search the documentation within R (or in RStudio), simply type <code>?</code> followed by the function name you’re using (more on functions coming soon). You can also search the documentation by typing two questions marks (<code>??SEARCH</code>).</p>
<ul>
<li><p>You can also look up help by using the <code>help()</code> function (e.g., <code>help(print)</code> will look up information on the <code>print()</code> function, just like <code>?print</code> does). There is also an <code>example()</code> function you can call to see examples of a function in action (e.g., <code>example(print)</code>). This will be more important in the next module!</p></li>
<li><p><a href="https://www.rdocumentation.org/">rdocumentation.org</a> has a lovely searchable and readable interface to the R documentation.</p></li>
</ul></li>
</ol>
</div>
<div id="resources-4" class="section level2 unnumbered">
<h2>Resources</h2>
<ul>
<li><a href="http://style.tidyverse.org/">Tidyverse Style Guide</a></li>
<li><a href="http://www.r-tutor.com/r-introduction">R Tutorial: Introduction</a></li>
<li><a href="http://www.r-tutor.com/r-introduction/basic-data-types">R Tutorial: Basic Data Types</a></li>
<li><a href="https://www.tutorialspoint.com/r/r_operators.htm">R Tutorial: Operators</a></li>
<li><a href="https://support.rstudio.com/hc/en-us/articles/200711853-Keyboard-Shortcuts">RStudio Keyboard Shortcuts</a></li>
<li><a href="https://www.rdocumentation.org/">R Documentation</a> searchable online documentation</li>
<li><a href="http://r4ds.had.co.nz/">R for Data Science</a> online textbook, oriented
toward R usage in data processing and visualization</li>
<li><a href="http://arrgh.tim-smith.us/">aRrgh: a newcomer’s (angry) guide to R</a> opinionated but clear introduction</li>
<li><a href="https://www.nostarch.com/artofr.htm">The Art of R Programming</a> print textbook</li>
</ul>

</div>
</div>
            </section>

          </div>
        </div>
      </div>
<a href="git-basics.html" class="navigation navigation-prev " aria-label="Previous page"><i class="fa fa-angle-left"></i></a>
<a href="functions.html" class="navigation navigation-next " aria-label="Next page"><i class="fa fa-angle-right"></i></a>
    </div>
  </div>
<script src="libs/gitbook-2.6.7/js/app.min.js"></script>
<script src="libs/gitbook-2.6.7/js/lunr.js"></script>
<script src="libs/gitbook-2.6.7/js/plugin-search.js"></script>
<script src="libs/gitbook-2.6.7/js/plugin-sharing.js"></script>
<script src="libs/gitbook-2.6.7/js/plugin-fontsettings.js"></script>
<script src="libs/gitbook-2.6.7/js/plugin-bookdown.js"></script>
<script src="libs/gitbook-2.6.7/js/jquery.highlight.js"></script>
<script>
gitbook.require(["gitbook"], function(gitbook) {
gitbook.start({
"sharing": {
"github": true,
"facebook": false,
"twitter": false,
"google": false,
"linkedin": false,
"weibo": false,
"instapaper": false,
"vk": false,
"all": ["github", "facebook", "twitter", "google"]
},
"fontsettings": {
"theme": "white",
"family": "sans",
"size": 2
},
"edit": {
"link": "https://github.com/info201/book/edit/master/r-intro.Rmd",
"text": "Edit"
},
"history": {
"link": null,
"text": null
},
"download": null,
"toc": {
"collapse": "section",
"scroll_highlight": true
}
});
});
</script>

</body>

</html>