Replace diagonal elements only in rows specified by a vector of row indices? (MATLAB)

Question

I have an N x N matrix, A, and a vector of row indices, v. I want to replace the diagonal elements of A only for the rows in A specified by v without using a for loop.

For example:

N = 10; A = rand(N,N); %Random N x N matrix v = [1 4 6 9 10]; %vector of row indices %What I want to do but without a for loop: for i = 1:length(v) A(v(i),v(i)) = 0; end %I thought this would work, but it does not: %A(v,v) = 0;

I feel like there must a one-line method of doing this, but can't seem to figure out what it would be.

Cheers

Phil Goddard · Accepted Answer · 2018-04-26 18:13:32Z

5

Use sub2ind:

A(sub2ind(size(A),v,v)) = 0;

answered Apr 26, 2018 at 18:13

Phil Goddard

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