MATLAB: Replace non-zero elements in array with output of a calculation on them

Question

Hi,

I have an array, A = [2 3 0 7 0 0 9].

How can I replace the non-zero elements of A with thier original value minus one?

I want to generate B = [ 1 2 0 6 0 0 8]

Any help would be appreciated! Thanks,

DB

Answer 1

mask = A~=0;
A(mask) = A(mask) - 1;

You can code it as a single expression, but that risks evaluating the comparison twice:

A(A~=0) = A(A~=0) - 1;