How to convert all array values into negative ones?

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Lu Da Silva
Lu Da Silva el 31 de En. de 2022
Editada: John D'Errico el 31 de En. de 2022
I have an array A:
A = [2; 3; 5; -8; 9; 1; -1]
how do I convert it into an array whose values are all negative? So as to obtain B:
A = [-2; -3; -5; -8; -9; -1; -1]
Thanks!

Respuesta aceptada

KSSV
KSSV el 31 de En. de 2022
A = [2; 3; 5; -8; 9; 1; -1] ;
A(A>0) = -A(A>0)
A = 7×1
-2 -3 -5 -8 -9 -1 -1

Más respuestas (3)

Burhan Burak AKMAN
Burhan Burak AKMAN el 31 de En. de 2022
You can do like.
A = [2; 3; 5; -8; 9; 1; -1];
A = -(A.*A).^0.5;
A = 7×1
-2 -3 -5 -8 -9 -1 -1

Walter Roberson
Walter Roberson el 31 de En. de 2022
A = [2; 3; 5; -8; 9; 1; -1]
A = 7×1
2 3 5 -8 9 1 -1
%way #1
A(A>0) = -A(A>0)
A = 7×1
-2 -3 -5 -8 -9 -1 -1
%way #2
A = [2; 3; 5; -8; 9; 1; -1]
A = 7×1
2 3 5 -8 9 1 -1
A = -abs(A)
A = 7×1
-2 -3 -5 -8 -9 -1 -1

John D'Errico
John D'Errico el 31 de En. de 2022
Editada: John D'Errico el 31 de En. de 2022
So many ways. Don't forget the simple solution:
A = [2; 3; 5; -8; 9; 1; -1]
A = 7×1
2 3 5 -8 9 1 -1
B = -abs(A) % this makes all of the signs positive, then negates the entire lot
B = 7×1
-2 -3 -5 -8 -9 -1 -1
Or we could do this:
C = -sign(A).*A % this is similar to the use of abs
C = 7×1
-2 -3 -5 -8 -9 -1 -1
Those ways act on the entire array. In order to act only on those that have the wrong sign and do it effectively in place, the standard MATLAB solution would be this:
A(A > 0) = -A(A > 0)
A = 7×1
-2 -3 -5 -8 -9 -1 -1

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