Python numpy 中的标准差
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Standard deviation in numpy
提问by user1700890
Here is my code:
这是我的代码：
import numpy as np
print(np.std(np.array([0,1])))
it produces 0.5
它产生 0.5
I am confident that this is incorrect. What am I doing wrong?
我相信这是不正确的。我究竟做错了什么？
采纳答案by Mad Physicist
By default, numpy.stdreturns the population standard deviation, in which case np.std([0,1])is correctly reported to be 0.5. If you are looking for the sample standard deviation, you can supply an optional ddofparameter to std():
默认情况下，numpy.std返回总体标准差，在这种情况下np.std([0,1])正确报告为0.5。如果您正在寻找样本标准偏差，您可以提供一个可选ddof参数std()：
>>> np.std([0, 1], ddof=1)
0.70710678118654757
ddofmodifies the divisor of the sum of the squares of the samples-minus-mean. The divisor is N - ddof, where the default ddofis 0as you can see from your result.
ddof修改样本减去均值的平方和的除数。除数是N - ddof，默认值ddof是0您从结果中看到的。
