#10670: Mobius matrices of posets are integer matrices
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Reporter: chapoton | Owner: sage-combinat
Type: defect | Status: new
Priority: minor | Milestone:
Component: combinatorics | Keywords: poset, matrix
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Description changed by chapoton:
Old description:
> I have noticed the following problem.
> {{{
> P=Posets.PentagonPoset()
> P.mobius_function_matrix().parent()
> Full MatrixSpace of 5 by 5 sparse matrices over Rational Field
> }}}
> The Mobius function of a poset should really be an '''integer matrix'''.
New description:
I have noticed the following problem.
{{{
P=Posets.PentagonPoset()
P.mobius_function_matrix().parent()
Full MatrixSpace of 5 by 5 sparse matrices over Rational Field
}}}
The Mobius function of a poset should really be an '''integer matrix'''.
This can be achieved by using change_ring :
{{{
P.mobius_function_matrix().change_ring(ZZ).parent()
Full MatrixSpace of 5 by 5 sparse matrices over Integer Ring
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10670#comment:2>
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