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.
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. 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