A^k for matrix multiplication in R?

Question

Suppose A is some square matrix. How can I easily exponentiate this matrix in R?

I tried two ways already: Trial 1 with a for-loop hack and Trial 2

Answer 1

A shorter solution with eigenvalue decomposition:

"%^%" <- function(S, power)
         with(eigen(S), vectors %*% (values^power * t(vectors)))