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FreeMat
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Section: Elementary Functions
Computes the variance of an array along a given dimension. The general syntax for its use is
y = var(x,d)
where x is an n-dimensions array of numerical type. The output is of the same numerical type as the input. The argument d is optional, and denotes the dimension along which to take the variance. The output y is the same size as x, except that it is singular along the mean direction. So, for example, if x is a 3 x 3 x 4 array, and we compute the mean along dimension d=2, then the output is of size 3 x 1 x 4.
The output is computed via
where
If d is omitted, then the mean is taken along the first non-singleton dimension of x.
The following piece of code demonstrates various uses of the var function
--> A = [5,1,3;3,2,1;0,3,1] A = 5 1 3 3 2 1 0 3 1
We start by calling var without a dimension argument, in which case it defaults to the first nonsingular dimension (in this case, along the columns or d = 1).
--> var(A)
ans =
6.3333 1.0000 1.3333
Next, we take the variance along the rows.
--> var(A,2)
ans =
4.0000
1.0000
2.3333