How can i change values in matrix in random fashion?

i have this matrix

p=[1 -1 -1 -1 -1 1 -1;
   1 1 1 -1 -1 1 -1]

how can i randomly change the values at any two positions in this matrix.

note : random numbers are to be either 1 or -1

Answer 1

[Cris LaPierre]

I'd use numel, and randi to identify 2 random points, and then, using linear indexing, multipy those 2 points by -1.

[Steven Lord]

You probably want randperm not randi so you don't swap a point with itself. You don't want to reverse the polarity of the neutron flow if it's already had its polarity reversed; that would confuse the polarity!

[Cris LaPierre]

Good catch.