How do I convert a n*1 matrix to a n*n diagonal matrix

Question

I have a nx1 matrix I want to convert this to a nxn diagonal matrix in R

Answer 1

If you just want to know how to do this in R, it's:

my.matrix       <- matrix(0, nrow=4, ncol=4)
diag(my.matrix) <- rep(0.25, 4)