Convert integer to logical array in MATLAB

Question

I want to convert an integer i to a logical vector with an i-th non-zero element. That can de done with 1:10 == 2, which returns

0              


        

Answer 1

You can use bsxfun:

>> bsxfun(@eq, 1:10, [2 5].')
ans =

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

Note the transpose .' on the second vector; it's important.

Answer 2

Another way is to use eye and create a logical matrix that is n x n long, then use the indices to index into the rows of this matrix:

n = 10;
ind = [2 5];

E = eye(n,n) == 1;
out = E(ind, :);

We get:

>> out

out =

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

Answer 3

Just another possibility using indexing:

n = 10;
ind = [2 5];
x=zeros(numel(ind),n);
x(sub2ind([numel(ind),n],1:numel(ind),ind))=1;