Re: don't understand matrix-multiplication should be reversed in python?

From	Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups	comp.lang.python
Subject	Re: don't understand matrix-multiplication should be reversed in python?
Date	2015-11-14 13:12 +1300
Message-ID	<dancjaFn10oU1@mid.individual.net> (permalink)
References	<ecc7eec6-3298-4f80-9bfb-eeecd3eeeb3a@googlegroups.com> <mailman.280.1447365421.16136.python-list@python.org> <11344ffd-f594-4059-8c41-6bacbdb66f10@googlegroups.com> <mj2c4b55qf6cfcbsh96465lmah3908hjpv@4ax.com>

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Dave Farrance wrote:
> Yep, he's evidently used to the Matlab/Octave way of defining "vectors"
> which is somewhat easier for a math-oriented interactive environment.
> 
> It's just a *bit* more laborious to append columns in numpy.

Yes, that's probably the main reason to do things that way.
A collection of vectors is most conveniently represented as
a 2D array where the first index selects one of the vectors.
But then to apply a transformation matrix to all the vectors,
you need to transpose the matrix and multiply it on the
right.

-- 
Greg

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don't understand matrix-multiplication should be reversed in python? PythonDude <mjoerg.phone@gmail.com> - 2015-11-12 07:57 -0800
  Re: don't understand matrix-multiplication should be reversed in python? Ian Kelly <ian.g.kelly@gmail.com> - 2015-11-12 09:34 -0700
    Re: don't understand matrix-multiplication should be reversed in python? PythonDude <mjoerg.phone@gmail.com> - 2015-11-13 00:56 -0800
  Re: don't understand matrix-multiplication should be reversed in python? Robert Kern <robert.kern@gmail.com> - 2015-11-12 21:56 +0000
    Re: don't understand matrix-multiplication should be reversed in python? PythonDude <mjoerg.phone@gmail.com> - 2015-11-13 00:57 -0800
      Re: don't understand matrix-multiplication should be reversed in python? Dave Farrance <df@see.replyto.invalid> - 2015-11-13 16:35 +0000
        Re: don't understand matrix-multiplication should be reversed in python? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-11-14 13:12 +1300

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