Reduces a matrix to its distinct rows and gives the number of replications of each row in the original dataset. An optional second matrix y can be given, the rows of y are summed up accordingly.
Calculates the symmetric root of a symmetric positive semidefinite matrix,(s.p.s.d.) ie. symroot(x)=symroot(x)' and symroot(x)*symroot(x) = x. uesful for simulation of multivariate normal variates with a given Covariance Structure
calculates the diagonal elements of a projection matrix X(X'X)^(-1) X' or (diag(w)^(1/2))X(X'diag(w)X)^(-1) X'diag(w)^(1/2); the calculation may be performed with a weight vector W.