Tools Numpy usecase bincount

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numpy 统计数组数值

numpy.bincount(x, weights=None, minlength=0)

• x 需要是一维数组 + 非负整数
• weights 每个位置的权重，维度同 x
• minlength 输出最小shape
• Output 最大值为 80, 输出[0,1,2....,80] 的统计值

上例中 minlength 可以设置 大于 80 的值，小于无效

UseCase

import numpy as np
data = np.array([1,1,1,1,1,1,2,3,5,4,4,4,5,80])
np.bincount(data.astype(np.int8))

array([0, 6, 1, 1, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1])

• minlength > max value

np.bincount(data.astype(np.int8), minlength=90)

array([0, 6, 1, 1, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0,
       0, 0])

• image

np.bincount(img.flatten())

Reference

• numpy.bincount()

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