On Tue, Aug 2, 2011 at 9:00 AM, Matthew Rocklin <mrock...@gmail.com> wrote: > Will do! > As a disclaimer I don't actually teach Linear Algebra (though I respect > those who do). The narratives posted are fictitious. I'm hypothesizing why > people might want Matrix Expressions.
That's a little misleading. Maybe you should put them in the second person. Aaron Meurer > > On Tue, Aug 2, 2011 at 9:58 AM, Alan Bromborsky <abro...@verizon.net> wrote: >> >> On 08/02/2011 10:10 AM, Matthew Rocklin wrote: >> >> Start of a wiki-page is here if people want to go this route. I put down >> the things that I think about. >> https://github.com/sympy/sympy/wiki/Matrix-Expressions >> I'm also happy to continue the conversation over e-mail. >> What would be a good next step? How can I stimulate activity on this >> topic? >> >> On Sat, Jul 30, 2011 at 8:02 AM, Matthew Rocklin <mrock...@gmail.com> >> wrote: >>> >>> I see that Andy just posted while I was writing. I'll post anyway >>> although Ii thnk maybe the wiki page is a better start. >>> It seems like we have a few people who want to contribute to the same >>> concept. Should we put something on the master branch so that people can >>> start adding to it? >>> What would a general framework for matrix expressions look like that >>> could handle most of the use-cases? What are the use cases? So far we have >>> >>> Expression that may contain matrices as atomic symbols >>> Expression that may contain immutable matrices >>> Derivatves of symbols >>> Derivatves over indices? >>> Block matrices >>> >>> On Sat, Jul 30, 2011 at 1:40 AM, Tim Lahey <tim.la...@gmail.com> wrote: >>>> >>>> On Sat, Jul 30, 2011 at 2:31 AM, Mateusz Paprocki <matt...@gmail.com> >>>> wrote: >>>> >>>> > I'm sure that, sooner or later, those approaches will have to be >>>> > merged, >>>> > because those are really two views of a very similar (if not the same) >>>> > problem domain. My original motivation came from reading lecture notes >>>> > for undergraduates about the finite element method. As usually there >>>> > was an >>>> > introduction to basics of algebra needed to understand the later >>>> > material, >>>> > and my question was why it must be so hard to do it in SymPy (if >>>> > possible at >>>> > all). My branch is about "symbolic matrices" with explicit content. >>>> > However, >>>> > I don't see any problem with allowing transition between those two >>>> > views >>>> > (well at least in one direction). Suppose we have expr = Eq(A*x, b), >>>> > where >>>> > A, x, b are matrices/vectors of appropriate shape. First, I would like >>>> > to be >>>> > able to manipulate the expression alone, check various shapes (and ask >>>> > SymPy >>>> > if it makes sense), etc. Then I would like to write something like >>>> > expr.expand(fullform=True) and get the same but with MatrixExpr with >>>> > explicit indexed symbols or values (if entities like zeros or ones >>>> > matrix >>>> > was used in expr). Then I would like to make further transformation on >>>> > this >>>> > "full form". >>>> >>>> I would like to do things like differentiate c^T*A*c with respect to >>>> the vector c. It's a common thing for finite elements. But I'd also >>>> like block matrices. However, if you have symbolic matrix expressions, >>>> you can put them in a matrix and then perform standard matrix >>>> calculations on that and you'd have block matrix support. So, as long >>>> as that's possible, there's no problem. >>>> >>>> I've got by handling differentiating matrix-vector expressions in >>>> Maple using their non-commutative support along with hacking together >>>> handling the transpose and differentiation of it. But, I'd like proper >>>> support. >>>> >>>> If Sympy could support block matrices, that would be extremely useful >>>> in control theory (where they're used all the time). >>>> >>>> Cheers, >>>> >>>> Tim. >>>> >>>> -- >>>> Tim Lahey >>>> PhD Candidate, Systems Design Engineering >>>> University of Waterloo >>>> http://about.me/tjlahey >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "sympy" group. >>>> To post to this group, send email to sympy@googlegroups.com. >>>> To unsubscribe from this group, send email to >>>> sympy+unsubscr...@googlegroups.com. >>>> For more options, visit this group at >>>> http://groups.google.com/group/sympy?hl=en. >>>> >>> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To post to this group, send email to sympy@googlegroups.com. >> To unsubscribe from this group, send email to >> sympy+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/sympy?hl=en. >> >> I looked at your wiki page and since you teach linear algebra you might >> find the following book interesting - >> >> >> http://www.amazon.com/Linear-Geometric-Algebra-Alan-Macdonald/dp/1453854932 >> >> also if you have not already done so you should look at the documentation >> for the geometric algebra module for sympy. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To post to this group, send email to sympy@googlegroups.com. >> To unsubscribe from this group, send email to >> sympy+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/sympy?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to sympy@googlegroups.com. > To unsubscribe from this group, send email to > sympy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sympy?hl=en. > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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