Opened 11 years ago

Last modified 5 years ago

#5201 new enhancement

make solve understand matrix equations

Reported by: jason Owned by: burcin
Priority: major Milestone: sage-wishlist
Component: calculus Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description

I think it would be a great thing if solve could recognize matrices and that two matrices are equal if each entry is equal. I believe MMA does this (but it's easier there; matrices are nothing more than nested lists). It'd certainly make certain things I do more natural if I could do:

solve(matrixA==matrixB)

and that was equivalent to:

solve([i==j for i,j in zip(matrixA.list(), matrixB.list())])

Okay, so now that I've written my piece, I suppose the next step is to open a trac ticket, write a patch to implement it, and post it for review :).

Change History (10)

comment:1 Changed 11 years ago by mabshoff

  • Milestone changed from sage-3.4 to sage-3.4.1

Which part of no non-ReST tickets against 3.4 is hard to understand? :p

Cheers,

Michael

comment:2 Changed 11 years ago by jason

argh! I looked at the list and thought "the first item is the ReST transition, so I have to pick the second item". Apparently I was thinking that the next release was already out and 3.3 was the ReST transition.

comment:3 Changed 10 years ago by jason

  • Keywords beginner added
  • Report Upstream set to N/A

comment:4 Changed 9 years ago by ryan

Could this be accomplished by overriding the comparison operator for the matrix class?

for example

def __richcmp__(self, other_matrix, cmptype):
  if cmptype == 2:  #this is the '==' operator
    if is_Matrix(other_matrix):
      if False in [i==j for i,j in zip(self.list(), other_matrix.list())]:
        return False
      else: return True

I'm just not sure where the 'matrix class' is. This would allow comparisons like

sage: matrixA == matrixB
True

comment:5 Changed 9 years ago by jason

  • Keywords beginner removed

You bring up a good point, and make me doubt whether the feature request is even feasible. Certainly it's probably not a beginner ticket after all. The problem is that we already have an == operator:

sage: a=matrix(SR,2,[x,x^2,x+1,x+4])
sage: b=matrix(SR,2,[4,3,2,1])
sage: a==b
False

That means that all solve will see is False. Instead, we want something like:

sage: SR(a)==SR(b)
([    x   x^2]
[x + 1 x + 4]) == ([4 3]
[2 1])

(i.e., we want the == in the solve to construct an equation, which it does for symbolic objects. One of the issues at heart here is that a symbolic object wrapping a Sage matrix is different from a Sage matrix containing symbolic objects.

So I'm going to take off beginner status for this ticket here. It would still be nice if solve(SR(a)==SR(b)) worked in the above example.

comment:6 Changed 6 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:7 Changed 6 years ago by vbraun_spam

  • Milestone changed from sage-6.1 to sage-6.2

comment:8 Changed 6 years ago by vbraun_spam

  • Milestone changed from sage-6.2 to sage-6.3

comment:9 Changed 5 years ago by vbraun_spam

  • Milestone changed from sage-6.3 to sage-6.4

comment:10 Changed 5 years ago by rws

  • Milestone changed from sage-6.4 to sage-wishlist
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