Assignment and accessing using indices

I had a question about how to do a particular type of assignment using indices. The code below is a simplified example.

k = zeros(4,4);
v = [2,3];
k(v,v) = 1;

My intention was to get a result that looks like

ans =
[0, 0, 0, 0;
 0, 1, 0, 0;
 0, 0, 1, 0;
 0, 0, 0, 0]

But unfortunately the result is:

ans =
[0, 0, 0, 0;
 0, 1, 1, 0;
 0, 1, 1, 0;
 0, 0, 0, 0]

So my question is: Is there a way to access individual elements (rather than rectangular regions) without using a for loop (Which I understand is computationally expensive in MatLab)?

Answer 1

[Azzi Abdelmalek]

k = zeros(4,4);
v = [2,3];
idx=sub2ind(size(k),v,v)
k(idx) = 1;

[Jeff Wood]

Thanks,

I should have mentioned that v might be different for rows and columns (i.e. I was using the generic case where they were the same).

Answer 2

[John BG]

diag([0 1 1 0])

John

[e-mail]

Answer 3

[Chad Greene]

Try this:

A = zeros(4); 
lin = sub2ind([4 4],2:3,2:3);
A(lin) = 1;