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

This is not something I've used before, but according to this handy dandy Matlab to R cheat sheet, you might try something like this, where m is the number of rows in the matrix, r and c are row and column numbers respectively, and ind the linear index:

MATLAB:

[r,c] = ind2sub(size(A), ind)

R:

r = ((ind-1) %% m) + 1
c = floor((ind-1) / m) + 1

MATLAB:

ind = sub2ind(size(A), r, c)

R:

ind = (c-1)*m + r