Is there a better way to implement this MATLAB code?

Question

Y = zeros(5000,10); y is a 5000 x 1 predefined vector consisting of numbers from 1 to 10;

for i= 1:size(Y,1)
    Y(i,y(i)) = 1;
end

Is there a better and simpler way to implement this since the rest of my code is vectorized and does not contain any for loop

Answer 1

You could use bsxfun:

bsxfun(@eq,y,[1:10])

Instead of your code, you can create each row using y(i)==[1:10] which is finally wrapped in bsxfun to vectorize.

Another idea would be index calculation:

Y((y-1).*5000+(1:5000).')=1;

Answer 2

You could use sub2ind:

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

However, this might actually be slightly slower:

Y = zeros(5000,10);
y = randi(10, 5000, 1);

tic
for jj = 1:1000
    for i = 1:size(Y,1)
        Y(i,y(i)) = 1;
    end
end
toc
% Elapsed time is 0.126774 seconds.

tic
for jj = 1:1000
    Y(sub2ind(size(Y), 1:size(Y, 1), y')) = 1;
end
toc
% Elapsed time is 0.139531 seconds.

% @Daniel's solution
tic
for jj = 1:1000
    Y = double(bsxfun(@eq, y, 1:10));
end
toc
%Elapsed time is 0.187331 seconds.