How can I set specific Elements of a Matrix to zero without a for loop

Here is my problem:

o= ones(3,3) % Given Matrix
o =

       1     1     1
       1     1     1
       1     1     1

i = [1 2 2]; % column index of o, which should be set to zero
             % quantity of rows in o is always exactly the same like length(i)

The result after manipulating matrix o depending on i should be:

o =

       0     1     1
       1     0     1
       1     0     1

My simple solution

for k=1:length(i)
    o(k,i(k))=0;
end

How can i do that without a for loop. In fact, the number of rows of matrix o is 10 000.

Thank you very much!

Answer 1

[Andrei Bobrov]

o= ones(3,3);
ii = [1 2 2]; 

[m,n] = size(o);
o(sub2ind([m,n],(1:m)',ii(:)')) = 0;

other way

n = 3;
out = ~accumarray([(1:n)',ii(:)],1,[3,3]) + 0;

[Immanuel Roßteutscher]

Great, thank you very much!

I changed

o(sub2ind([m,n],(1:m)',ii(:)') = 0;

into

 o(sub2ind([m,n],1:m,ii(:)')) = 0;

Because it seems that for

sub2ind(A,B,C)

B and C, always have to be column vectors.

Do you think sub2ind is faster conpared to using the for loop?

Not yet tried your second solution.