convert array A values to indices of array B

hi,

lets say I have a 10x10 array A with (4,4) = -2 and (6,6) = 2 . How would I construct an array B such that these values mean the shift in horizontal direction, e.g array B is zeros, except B(4,2) = 2 and B(6,8) = -2 ?

many thanks!

Answer 1

[Guillaume]

Possibly, this is what you want, although it's not clear where the values to go in B come from:

A = zeros(10);
A(4, 4) = -2;
A(6, 6) = 2;

[r, c] = find(A); %find original coordinates of non zero values
c = c + nonzeros(A); %shift by value at coordinates
B = zeros(size(A));
B(sub2ind(size(B), r, c)) = -nonzeros(A) %are the values just the negative of the original ones?

[mb]

again Guillaume,

you saved my day!

many thanks!