Simple question about Standard Deviation.
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I have a number of data points, lets say in a vector v, and lets say there are "num" of them. If I write sd = std(v) did it assume a sample i.e. it used num-1 (in the denominator) or did I get a population standard dev i.e. it used num? How can I request one or the other?
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the cyclist
2017-1-8
编辑:the cyclist
2017-1-8
By default, it will give the sample standard deviation. Call it as
std(x,1)
to get the population. That is explained in the documentation for std, in the section describing the input argument weight.
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Helen Kirby
2017-1-8
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Walter Roberson
2017-1-9
You cannot combine the two weighting schemes.
std(x) is normalized by N-1. std(x,1) is normalized by N. std(x,1) works out to be the same as std(x, ones(size(x)) .
std(x,w,1) means to proceed along dimension 1. Your data was row vectors, so that did not work. But you could use
std(x(:), w(:), 1)
if you had particular reason for wanting to specifically process along the first dimension.
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