How to make Triu in reverse axis for triangular matrices ?

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Ramesh Bala
Ramesh Bala 2020-12-2
评论： Ramesh Bala 2020-12-2
The function triu makes the upper triangular matrix in the shape of L . How shall I reverse it like to make it run in opposite diirection.
The below function make triu in the top to bottom,i wanna to make it bottom to top and thus reversing it ?
A = ones(6);
idx = ( A(:,3:end) );
A(:,3:end) = triu(idx,-1)

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John D'Errico
John D'Errico 2020-12-2
Ran in:
Are you asking to do no more than this?
A = magic(6)
A = 6×6
35 1 6 26 19 24 3 32 7 21 23 25 31 9 2 22 27 20 8 28 33 17 10 15 30 5 34 12 14 16 4 36 29 13 18 11
●
A = flip(tril(flip(A)))
A = 6×6
35 1 6 26 19 24 3 32 7 21 23 0 31 9 2 22 0 0 8 28 33 0 0 0 30 5 0 0 0 0 4 0 0 0 0 0
●
That is a simple way to do it. There would be others.

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