Programmer Guide/Command Reference/EVAL/var

Compute the variance, covariance or covariance-matrix.

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Usage 1

var(xvector)

Result 1

The variance v of vector x.

v = sum( (x-avr(x))?^2 ) / (nrow(x)-1) = (x-avr(x)^2 / (ncol(x)-1)

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Usage 2

var(xvector, yvector)

Result 2

The covariance v of the vectors x and y.

v = sumi = 0..nrow(x) ( (xi-avr(x)) * (yi-avr(y)) ) / (nrow(x)-1)

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Usage 3

var(xmatrix)

var(xmatrix, yscalar)

var(xmatrix, yvector)

Result 3

The covariance matrix v of the column vectors of x.

vi,j = sumk = 0..nrow(x) ( (xk,i-ai) * (xk,j-aj) ) / (nrow(x)-1) , with: i,j = 0..ncol(x)

The column averages a_i=0..ncol(x) are computed as follows:

y not supplied	ai = avr(x*,i)
yscalar	ai = y
yvector	ai = yi

See also

avr, dev, corr

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