Converting between matrix subscripts and linear indices (like ind2sub/sub2ind in matlab)

Question

Let\'s say you have a matrix

m <- matrix(1:25*2, nrow = 5, ncol=5)

How do you go from matrix subscripts (row index, column index) to a lin

Answer 1

You mostly don't need those functions in R. In Matlab you need those because you can't do e.g.

A(i, j) = x

where i,j,x are three vectors of row and column indices and x contains the corresponding values. (see also this question)

In R you can simply:

A[ cbind(i, j) ] <- x