A = [3 5 -4; -8 -1 33; -17 6 -9]
[rows,columns] = size(A);
for i = 1:rows
    for j = 1:columns

        if A(i,j) >= 1
        B(i,j) = log(A(i,j)) + 20 ;
        else
        B(i,j) = A(i,j);
        end

    end
end
B