Is there a way to vectorize the definition of this matrix ?

I am defining the matrix z this way :

z=zeros(n,m);
for i=1:n
    for j=1:m
        z(i,j)= i==y(j);
    end
end 

where y is a vector of size m. Is there a better way to write this ? (one line maybe)

Answer 1

[Turlough Hughes]

Here's one way to do it in one line:

z = y.*ones(n,m)==(1:n).'.*ones(n,m);

I tested with the following inputs:

y=1:10;
n=5; m=length(y);
z = y.*ones(n,m)==(1:n).'.*ones(n,m);

edit: following stephens comment.

[Stephen23]

Note that square brackets are a concatentation operator, and should be replaced with grouping parentheses (exactly as the hint in the MATLAB editor also tells you):

(1:n)

It is a good habit to use transpose instead of conjugate transpose (unless you really need the conjugate transpose):

(1:n).'

[Turlough Hughes]

Thanks Stephen.