Change the sign of a particular element in a matrix

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Pranjal Pathak
Pranjal Pathak 2012-12-28
Hi, I have a problem in the following matrix: A=[ -1 1 0 0 0 0; 0 -1 1 0 0 0 ; 0 0 -1 1 0 0; 0 0 0 0 -1 1 ; 0 0 0 0 0 -1 ; 0 0 0 0 0 0];
In the above matrix, I need to change only the element -1 by +1, while others remaining the same. For, small matrix, it is possible by defining the row and column elements but for large matrix, is there any way of doing it programatically in matlab as the dimension of the matrix may be larger than this. Please help me in this regard.
Thanking You!

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采纳的回答

Muruganandham Subramanian
编辑：Jan 2012-12-28
find(A==-1)=1
[EDITED, Jan, copied from comments] Better: A(A==-1)=1;
or
A=abs(A)

更多回答（1 个）

Image Analyst
Image Analyst 2012-12-28
What do you mean change it by +1? Do you mean change it TO +1, or change it by +1 by adding +1 to the -1 so that you get 0? Here's three different ways to do the two possible meanings of your question:
A = [ -1 1 0 0 0 0; 0 -1 1 0 0 0 ; 0 0 -1 1 0 0; 0 0 0 0 -1 1 ; 0 0 0 0 0 -1 ; 0 0 0 0 0 0]
A(A == -1) = 1
A = [ -1 1 0 0 0 0; 0 -1 1 0 0 0 ; 0 0 -1 1 0 0; 0 0 0 0 -1 1 ; 0 0 0 0 0 -1 ; 0 0 0 0 0 0]
A(A == -1) = 0
A = [ -1 1 0 0 0 0; 0 -1 1 0 0 0 ; 0 0 -1 1 0 0; 0 0 0 0 -1 1 ; 0 0 0 0 0 -1 ; 0 0 0 0 0 0]
elementsToChange = A == -1;
A(elementsToChange) = A(elementsToChange) + 1
  2 个评论
Shaun VanWeelden
Shaun VanWeelden 2012-12-28
Image Analyst, your always so thorough in your answers, I love it
Jan
Jan 2012-12-28
@Shaun: You can vote this answer, if you find it useful.

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