Pollutant.R

pollutantmean <- function(directory, pollutant, id) {
        ## 'directory' is a character vector of length 1 indicating the location of
        ## the CSV files
        
        ## 'pollutant' is a character vector of length 1 indicating the name of the
        ## pollutant for which we will calculate the mean; either 'sulfate' or
        ## 'nitrate'.
        
        ## 'id' is an integer vector indicating the monitor ID numbers to be used
        
        ## Return the mean of the pollutant across all monitors list in the 'id'
        ## vector (ignoring NA values)
        data = numeric()
        for (i in id) {
                
                newRead = read.csv(paste(directory, "/", formatC(i, width = 3, flag = "0"), 
                                         ".csv", sep = ""))
                
                data = c(data, newRead[[pollutant]])
        }
        return(mean(data, na.rm = TRUE))
        print (mean(data, na.rm = TRUE))
}
pollutantmean("specdata", "nitrate", 23)