How to avoid using a loop here?

Hello. I want to do the same thing without a loop.

A = zeros(N);
for m = 1:N
    for n = 1:N
        A(m, n) = 2*N + 1 - (m + n);
    end
end

Answer 1

[Star Strider]

One approach —

N = 5;
tic
[m,n] = ndgrid(1:N);
A = 2*N + 1 - (m + n)

A = 5×5

9 8 7 6 5 8 7 6 5 4 7 6 5 4 3 6 5 4 3 2 5 4 3 2 1

toc

Elapsed time is 0.047132 seconds.

Compare —

tic
A = zeros(N);
for m = 1:N
    for n = 1:N
        A(m, n) = 2*N + 1 - (m + n);
    end
end
toc

Elapsed time is 0.003632 seconds.

A

A = 5×5

9 8 7 6 5 8 7 6 5 4 7 6 5 4 3 6 5 4 3 2 5 4 3 2 1

The nested loops are actually faster!

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