calculate the variance over non %nan values
m=nanvar(X,dim)
* X = a (n x k) real matrix
* dim = the orientation over which variance is calculated
* m = a scalar or vector collecting the variance over non %nan values
X=[%nan , 1 , %nan ;... %nan , 3 , 2;... %nan , 5 , 4 ] y=nanvar(X) // provides y=2.5 y=nanvar(X,'r') // provides y=[%nan,4,2] y=nanvar(X,'c') // provides y=[%nan;0.5;0.5]