Return logical for rows of non-zero numbers for specified columns (similar to "all" function)

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BobbyRoberts
BobbyRoberts on 10 Aug 2021
Commented: Matt J on 10 Aug 2021
Hi. I need to calculate a logical from a 1x3 matrix (although the number of columns is irrelevant) that tells me if non-zero numbers are in specified columns.
For example, if I have the following matrix callled mat:
4 16 2
6 7 7
1 4 8
0 5 19
3 0 5
9 0 16
x = all(mat,2)
x here would return a logical array where each row equaling "1" will have ALL non-zero numbers. In mat, this would only be the first 3 rows, and thus x = [1 1 1 0 0 0];
My question is whether there is an easy line of code or existing function that would allow me to specifiy which columns I would like to be non-zero in order for the logical to spit out a ero. For example, if I wanted all rows where columns 1 and 3 are non-zero, the logical that is returned should be something like this: x = [0 0 0 0 1 1] since only the last two rows fit that criteria.
Or if I wanted all rows where columns 2 and 3 were non-zero, it should return x = [0 0 0 1 0 0]
Thanks in advance!
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Matt J
Matt J on 10 Aug 2021
For example, if I wanted all rows where columns 1 and 3 are non-zero , the logical that is returned should be something like this: x = [0 0 0 0 1 1] since only the last two rows fit that criteria.
Why don't the first 3 rows fit the criteria? Shouldn't the result be x = [1,1,1 0 1 1]

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Accepted Answer

Matt J
Matt J on 10 Aug 2021
Edited:Matt J on 10 Aug 2021
For example, if I wanted all rows where columns 1 and 3 are non-zero
This would be,
all(mat(:,[1,3]),2)
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