Creating an array based on values in a vector

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John Jendzurski
John Jendzurski 2012-1-18
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!

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采纳的回答

Walter Roberson
Walter Roberson 2012-1-18
bsxfun(@eq,[1 1 3 2 3].',1:3)

更多回答（1 个）

the cyclist
the cyclist 2012-1-18
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;

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