var

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Compute the variance, covariance or covariance-matrix.


Usage 1
var(xvector)
Result 1
The variance v of vector x.
v = sum( (x-avr(x))?^2 ) / (nrow(x)-1)
v = (x-avr(x))^2 / (nrow(x)-1)

Usage 2
var(xvector, yvector)
Result 2
The covariance v of the vectors x and y.
v = sum( (x-avr(x) ?* (y-avr(y)) ) / (nrow(x)-1)
v = ((x-avr(x) * (y-avr(y))) / (nrow(x)-1)

Usage 3
var(xmatrix)
var(xmatrix, yscalar)
var(xmatrix, yvector)
Result 3
The covariance matrix v of the column vectors of x.
v[i,j] = sumk = 0..nrow(x) ( (xk,i-ai) * (xk,j-aj) ) / (nrow(x)-1) , with: i,j = 0..ncol(x)
The column averages ai=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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