MATLAB: Creating a matrix of ones and zeros with location of ones based on array value

Question

I need to acheive the following without a loop (for speed):

I have a vertical array where the value of each row tells me which column in a matrix of zeros should be replaced with a one.

For example, if I input:

y = [2; 3];

Then I want MATLAB to produce output:

Y = [0,1,0; 0, 0, 1];

I can acheive the desired output with the following for loop:

Y = zeros(2,3);
for j = 1:3
    Y(:,j) = (y==j);
end

In reality, my matrices are much larger and I want to avoid using for loops for speed. Is there anyway I can do this without a for loop?

Answer 1

One possible way is:

    Y = zeros(length(y), max(y));
    Y(sub2ind(size(Y), (1:length(y))', y)) = 1;