Use logical indexing to accomplish this:
A = [8 14 3; -13 1 42; -39 -8 15];
B = zeros(size(A));
Valid indices are those in which A is greater than 1,
vi = logical(A>1);
Where we found a logical "true", take the log of that location in A,
B( vi) = log(A(vi));
For the other indices, add 39 to them,
B(~vi) = A(~vi)+39;
Is this the output you were expecting?
B =
2.0794 2.6391 1.0986
26.0000 40.0000 3.7377
0 31.0000 2.7081
