Matrix Indexing

I have an index matrix.

idx = [1 5 ; 3 7 ]

The goal is to get a matrix like this:

1 0
0 0
0 1
0 0
1 0
0 0
0 1

Indexing the matrix like

a(idx) = 1;

doesn't work. Right now I use a loop, but I am not sure if this is the best way.

Answer 1

[Matt Fig]

A = zeros(max(idx(:)),size(idx,1));
A(sub2ind(size(A),idx,cumsum(ones(size(idx))))) = 1

[Joerg]

Thanks!