array with 1 and -1 - multiply coloums

Hello,

I have an array with a lot of -1 and 1.

Example:

-1 -1 -1 -1 -1

-1 1 -1 -1 -1

1 1 -1 1 -1

-1 -1 1 1 -1

I want to check if the row has 1 and if so if it has more than one 1. If I have more than one 1 in a row I want to multiply the columns for each row with a 1 and write the result into an new array.

For example:

The first row has no 1 > write in the new array 0

The second row has just one 1 in the second column > write the second column into a new array

The third row has a one in the first, second and fourth column > mulitply the three coloums and write the result into the new array

...

Thanks in advance for the answers!

[Jan]

What is the wanted output for the posted input? 1 matrix or 3 vectors?

What have you tried so far and which problems occur?

[Ma Hel]

I would be nice to get one matrix.

[Jan]

I assume the problem is solved by Voss' answer. But for your next question: It would be really helpful, if you do not only mention, that it is "one matrix" but post the manually created output for the shown input.

Answer 1

[Voss]

Like this?

M = [
    -1    -1    -1    -1    -1
    -1     1    -1    -1    -1
     1     1    -1     1    -1
    -1    -1     1     1    -1];

[n,m] = size(M);
new_arrays = repmat({zeros(n,1)},1,n);
for ii = 1:n
    idx = M(ii,:) == 1;
    if any(idx)
        new_arrays{ii} = prod(M(:,idx),2);
    end
end

new_arrays{:}

ans = 4×1

0 0 0 0

ans = 4×1

-1 1 1 -1

ans = 4×1

-1 1 1 1

ans = 4×1

1 1 -1 1

[Ma Hel]

Thank you very much! This is what I was looking for.

[Jan]

@Voss: I'm impressed! Thanks. I did not even understand the question.