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Partitioning a (1,-1)square matrix into (0,-1,1)summand matrices

asked 3 years ago

sgmth gravatar image

Given a square matrix M with entries from {1,-1} how to find all possible sets of matrices A1,A2,A3.....(with entries from {0,-1,1}), such that M=A1+A2+A3....

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Welcome to Ask Sage! Thank you for your question.

slelievre gravatar imageslelievre ( 3 years ago )

Do you require the matrices Aj to be pairwise distinct?

That way there would be finitely many tuples of matrices Aj summing to M.

One could also forbid having Aj=0 for any j, and forbid having Aj=Ak for any j and k.

slelievre gravatar imageslelievre ( 3 years ago )

Homework ?

Emmanuel Charpentier gravatar imageEmmanuel Charpentier ( 3 years ago )

Question refined at Ask Sage question 63305.

slelievre gravatar imageslelievre ( 2 years ago )

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answered 3 years ago

slelievre gravatar image

For each nonnegative integer k, you could find the possible tuples of matrices (A1,...,Ak) as follows:

  • for each of -1, 0, 1, find the ways to write it as a sum of k summands each in {-1, 0, 1}.

  • the target matrix M has n2 entries mi,j; so the (A1,...,Ak) are obtained by combining all the possible ways to get each entry.

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First of all apologies for replying very late as I was busy with some other things and I logged again yesterday only after so many months. I am really sorry for that. Yes, your idea of finding ways to write -1,0,1 as k summands of {-1,0,1} appears to be very good. i will try to make the code accordingly. Thanks a lot.

sgmth gravatar imagesgmth ( 2 years ago )

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Asked: 3 years ago

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Last updated: Jan 07 '22