How to scan a matrix and execute specific commands depending on value.

Let's say I had a 5x2 matrix:

0 1

1 0

1 1

1 0

0 1

I want to scan down the first column, and do the following:

• If the value is 0, I want to assign a 0 value to a new 5x1 matrix.
• If the value is >0, I want to move up a row and look at the value in the 2nd column.
• If the value in this 2nd column is 0, then assign a 0 to the new 5x1 matrix.
• If the value in this 2nd column is >0, then assign a 1 to the new 5x1 matrix.
• Continue through the rest of the matrix.

So, the output should look like this:

0

1

0

1

0

Many thanks!

[Walter Roberson]

What if the value is > 0 in the first column of the first line? "move up a row" would be moving to before the matrix.

[Laura Steel]

Hi, thanks for taking a look! The first value of the first column will always = 0, so this should not be a problem.

Answer 1

[Walter Roberson]

matrix = [0    1
1    0
1    1
1    0
0    1]

matrix = 5×2

0 1 1 0 1 1 1 0 0 1

if matrix(1,1)
    output1 = nan;    %his case is not defined, requires referring to row above first
else
    output1 = 0;
end
output2end = matrix(2:end,1) & matrix(1:end-1,2)

output2end = 4×1 logical array
   1
   0
   1
   0

output = [output1; output2end]

output = 5×1

0 1 0 1 0