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Graphical Linear Algebra

graphicallinearalgebra.net

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Re: Graphical Linear Algebra

#81

Earlier quoted context omitted.

Good visual explanations are useful to all learners. I'm sorry, but the concept of "visual learner" when used in contradistinction to "verbal learner" is just "lacks attention span to concentrate on something hard".

God forbid we show any kindness to people with attention deficits.

We should definitely be kind, to as many groups of people as humanly possible. But erecting artificial categories merely because someone thinks it will make some other subset of individuals feel better (a) is patronising to those people, and (b) introduces confusion for everyone.

Re: Graphical Linear Algebra

#82

I would like to read this but I really need a version without the verbiage and humour. I'm really not convinced it's necessary to try to make these things so "accessible".

Then read the paper that it's based on which is linked to by the blog and my other comments.

Thanks, I didn't mean to offend. Which is the best starting point? Based on the blog post I was hoping to get some introduction by way of familiar concepts such as linear algebra and homomorphism, before confronting applications to theoretical computer science. Anyway, is the best starting point "Diagrammatic Algebra: From Linear to Concurrent Systems" or "The Calculus of Signal Flow Diagrams I: Linear relations on streams" or something else?

Re: Graphical Linear Algebra

#83
post #44
post #30

Regardless of the usefulness of category theory or not, the author seems to imply that "traditional linear algebra" is about matrices. This is not true. This may be true from an engineering perspective, or maybe if you've studied in the US, but over here, linear algebra starts with fields, vector spaces, homomorphisms. We establish pretty early on that matrices and linear transformations are in essence the same thing…

Just curious, what country would this be? I know many European countries favor a more theoretical approach. I definitely learned linear algebra from the numerical and matrix perspective (though yes, we did cover the idea of vector spaces and linear transformations too). In engineering school, the focus tended to be on the craft rather than the theory, and in retrospect I think it was the right approach for engineerin…

I studied engineering with a European-style curriculum, which starts with groups, rings, vector spaces, linear transforms, eigenvalues, etc - and only then proved that matrices can be used to represent any finite dimensional to finite dimensional linear transformation, and mostly went on from there. It did seem roundabout at the time.

But then, everything was using the same terms, and was relatively simple and straightforward. Fourier transforms? Laplace Transforms? They are all just linear transformations. Functional analysis? It's a lot of inner products, hermitian forms and eigensystems but we were familiar with all the properties, so we only concerned outselves with what's different about it (e.g. the spectral theorem). Coding thoery? It's finite fields, we did those in linear algebra, now it's just applications. Stationary distributions on markov processes? It's application of linear algebra+probability, but works mostly the same whether it's discrete (and representable by a matrix) or continuous (when it isn't).

The syllabus for engineering students was basically the same as for math students, except we only covered proofs in class & homework (but did not have to be able to reproduce them in tests), and that we mostly went through a simple logical progression of ideas rather than a historical one (e.g., cauchy's theorem of analytic complex functions was essentially a two-line application of Green's theorem in the plane, and we spent ~30 minutes discussing it; math students spent ~6 weeks proving it in the way Cauchy historically did, progressing from simpler to complex structures)

Re: Graphical Linear Algebra

#84
I loved the Makelele story in the intro. I hardly remember him, and didn't recognize that Real was so much worse without him. Linalg really is the most underappreciated technique.

Re: Graphical Linear Algebra

#85
post #80

Earlier quoted context omitted.

Can you be more concrete?

A lot of category theory is just about composition, how different structures compose and how compositions of those structures continue to be composable. So in this case, GLA builds the theory of linear transformations from trivial/simple pieces and their various ways of being composed. It also discusses the mechanisms for proof and reduction (you noted how GLA is clear about whether a sub-computation is reused or not…

Well, that wasn't very concrete. How about this: can you give an example of a linear-algebraic fact that is more easily shown by reasoning about these diagrams than by just using the numbers-moving-along-wires interpretation to immediately turn it into regular equations?

For example, the only thing I can think of is maybe (AB)^T = B^T A^T.

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