Creating an array based on values in a vector

MATLAB gurus! Can ya'll help me with this one? I've got a column vector of integers ranging from 1 to N. I want to create an array with the same number of rows and N columns, where each element of a row is 'zero' except for a 'one' in the column corresponding to the integer in the row of the original vector. For example, consider N = 3 and given the column vector X = [1 1 3 2 3]'. I want to create the following array:

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

Obviously loops and so forth would accomplish this, but I am wondering if it can be done with just simple matrix algebra. Thanks!

Answer 1

[Walter Roberson]

bsxfun(@eq,[1 1 3 2 3].',1:3)

[John Jendzurski]

Wow. Very cool, Walter! I did not even know about bsxfun(). Thanks!!!

Answer 2

[the cyclist]

Here's one way:

N = 3;
X = [1 1 3 2 3]';

L = numel(X);

Y = zeros(L,N);

linearIndex = sub2ind([L,N],(1:L)',X);
Y(linearIndex) = 1;

[John Jendzurski]

Nice! I like this too. Thanks!