recursive residuals
[rresid]=recresid(y,x)
* y = dependent variable vector (n x 1)
* x = explanatory variables matrix (n x k)
* rresid = recursive residuals (first k-obs equal zero)
x=grand(40,3,'nor',0,1); y=x*ones(3,1)+grand(40,1,'nor',0,1); vv = recresid(y,x)