# "nchoosek" function for a matrix whose all elements are 0 or 1

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Ismaeel il 29 Dic 2016
Commentato: Ismaeel il 29 Dic 2016
I have a matrix A whose all elements are 0 or 1. For example, the first row of A is:
[ 0 0 1 0 0 1 0 1 0 0]
I want to use nchoosek function to find the combinations of (total number of 1's in a row) -1. Here, n= 3, k=n-1=2 (always k=n-1). How can I apply this function to all the rows of the matrix or at least, for the above vector.
The output should be as:
[ 0 0 1 0 0 1 0 0 0 0]
[ 0 0 1 0 0 0 0 1 0 0]
[ 0 0 0 0 0 1 0 1 0 0]
nchoosek (3,2)=3.
Thanks
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the cyclist il 29 Dic 2016
For the example
A = [0 0 1 0 0 1 0 1 0 0]
you want all possible rows that have two 1's and how many 0's?
Ismaeel il 29 Dic 2016
Thanks, yes all possible 1's without considering the 0's. But I want the locations of these possible 1's to be kept.

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### Risposta accettata

James Tursa il 29 Dic 2016
Modificato: James Tursa il 29 Dic 2016
E.g., using a loop:
f = find(A);
n = numel(f);
result = repmat(A,n,1);
for k=1:n
result(k,f(k)) = 0;
end
Or if the order matters:
result(k,f(n-k+1)) = 0;
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Ismaeel il 29 Dic 2016
So Cool, thank you so much James.
Ismaeel il 29 Dic 2016
Can we modify the code in case if A is a matrix instead of a vector? let's say: A=[0 0 1 0 0 1 0 1 0 0] [0 1 0 0 0 1 0 0 0 0] Thanks once again

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