how can i negative all value in a matrix except diagonal?

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arian hoseini
arian hoseini on 11 Jan 2022
Edited: Stephen23 on 11 Apr 2022
13.333 5 0 5 3.3333 0
5 27.333 4 10 3.3333 5
0 4 17.846 0 3.8462 10
5 10 0 17.5 2.5 0
3.3333 3.3333 3.8462 2.5 16.346 3.3333
0 5 10 0 3.3333 18.333

Accepted Answer

Stephen23
Stephen23 on 11 Jan 2022
Edited: Stephen23 on 11 Apr 2022
M = [13.333,5,0,5,3.3333,0;5,27.333,4,10,3.3333,5;0,4,17.846,0,3.8462,10;5,10,0,17.5,2.5,0;3.3333,3.3333,3.8462,2.5,16.346,3.3333;0,5,10,0,3.3333,18.333]
M = 6×6
13.3330 5.0000 0 5.0000 3.3333 0 5.0000 27.3330 4.0000 10.0000 3.3333 5.0000 0 4.0000 17.8460 0 3.8462 10.0000 5.0000 10.0000 0 17.5000 2.5000 0 3.3333 3.3333 3.8462 2.5000 16.3460 3.3333 0 5.0000 10.0000 0 3.3333 18.3330
Method one: subtraction (square only):
A = diag(diag(M)) - M.*~eye(size(M))
A = 6×6
13.3330 -5.0000 0 -5.0000 -3.3333 0 -5.0000 27.3330 -4.0000 -10.0000 -3.3333 -5.0000 0 -4.0000 17.8460 0 -3.8462 -10.0000 -5.0000 -10.0000 0 17.5000 -2.5000 0 -3.3333 -3.3333 -3.8462 -2.5000 16.3460 -3.3333 0 -5.0000 -10.0000 0 -3.3333 18.3330
Method two: indexing (more robust, should work for any size):
B = -M;
B(eye(size(M))==1) = diag(M)
B = 6×6
13.3330 -5.0000 0 -5.0000 -3.3333 0 -5.0000 27.3330 -4.0000 -10.0000 -3.3333 -5.0000 0 -4.0000 17.8460 0 -3.8462 -10.0000 -5.0000 -10.0000 0 17.5000 -2.5000 0 -3.3333 -3.3333 -3.8462 -2.5000 16.3460 -3.3333 0 -5.0000 -10.0000 0 -3.3333 18.3330

More Answers (1)

Jon
Jon on 11 Jan 2022
Am = -(A - diag(diag(A))) + diag(diag(A))

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