MATLAB: Use if / else inside a for-loop and change values of array depending on condition

Question

Hi all,

I am stuck with the following step and I can't find the solution. The code I need is to change the columns of an array depending on the column index. For odd numbers, without change, for even numbers change the sign.

The size of the array should be variable by dimensions 1 and 2.

Here is what I tryied. Can someone help me please.

Thanks

Size_1 = 5;
Size_2 = 6;
array = ones(Size_1,Size_2);
for i=1:Size_2    
    if rem(i,2)==0        
        new_array_2 = array(:,i);
    else
        new_array_2 = -1*array(:,i);
    end    
end

new_array should be this

new_array =

1 -1 1 -1 1 -1

1 -1 1 -1 1 -1

1 -1 1 -1 1 -1

1 -1 1 -1 1 -1

1 -1 1 -1 1 -1

Answer 1

No loops needed:

size1=5;
size2=6;
A=ones(size1,size2);
A(:,2:2:end)=-A(:,2:2:end)