R - return position of element in matrix?

Question

Given a matrix:

      [,1] [,2]
[1,]    0  0.0
[2,]   -1  0.8

What is the quickest way in R to iterate over the matrix and return the posit

Answer 1

m <- matrix(c(0, 1, 1, 0), nrow = 2)
which(m != 0)

or maybe

which(m != 0, TRUE)

Answer 2

Here is one approach

mat = matrix(rnorm(9), 3, 3)
which(mat !=0, arr.ind = T)