Simple question about Standard Deviation.
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Helen Kirby
am 8 Jan. 2017
Kommentiert: Walter Roberson
am 9 Jan. 2017
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
am 8 Jan. 2017
Bearbeitet: the cyclist
am 8 Jan. 2017
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
am 8 Jan. 2017
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Walter Roberson
am 9 Jan. 2017
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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