Indexing Diagonal Matrix Elements In Matlab
I have came across this problem very often, but always ended up solving it in a different way each time. Here is what looks to me to be the most concise way of doing it.
Indexing the diagonal
>> A = magic(4)
A =
16 2 3 13
5 11 10 8
9 7 6 12
4 14 15 1
>> A(1:length(A)+1:numel(A))
ans =
16 11 6 1
>> A(1:length(A)+1:numel(A)) = 1
A =
1 2 3 13
5 1 10 8
9 7 1 12
4 14 15 1Selecting off-diagonal entries
>> A = magic(4)
A =
16 2 3 13
5 11 10 8
9 7 6 12
4 14 15 1
>> A(setdiff(1:numel(A), 1:length(A)+1:numel(A))) = 0
A =
16 0 0 0
0 11 0 0
0 0 6 0
0 0 0 1
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