#10545: Add the outer product of two vectors
------------------------------+---------------------------------------------
Reporter: rbeezer | Owner: jason, was
Type: enhancement | Status: needs_review
Priority: minor | Milestone: sage-4.6.2
Component: linear algebra | Keywords:
Author: Rob Beezer | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Old description:
> Title pretty much says it all. Students frequently can't tell an inner
> product from an outer product (probably not too careful about where a
> transpose is). Maybe this will help.
>
> Depends on #10541
New description:
Title pretty much says it all. Students frequently can't tell an inner
product from an outer product (probably not too careful about where a
transpose is). Maybe this will help.
Depends on #10541
--
Comment(by rbeezer):
Hi Nils,
Thanks for the comments. Since vectors are neither rows nor columns in
Sage, any notion of a transpose is irrelevant. The outer product just is
what it is. I could delete the mention of the transpose in the
mathematical description in the docstring.
"Someone" are 19-year-old students, who shouldn't need to understand a
lambda function to learn linear algebra.
Sage can work well with a column-oriented approach - it just needs a few
things. Check out:
http://wiki.sagemath.org/devel/LatexToWorksheet
http://linear.ups.edu
Rob
Replying to [comment:2 nbruin]:
> I didn't know that is sometimes used as a definition of "outer product",
but Wikipedia backs you up on it.
>
> In other languages, "exterior product" translates to the same word as
"outer product", so a -1 from me for having this definition of outer
product. I think this term will be a source of confusion.
>
> If someone needs the tensor product, it is easy enough to get via the
one-liner
> {{{
> lambda v,w: matrix(len(v),len(w),[a*b for a in v for b in w])
> }}}
>
> (given Sage's preference for row vectors versus the preference of most
LA texts for column vectors, I expect that relating inner/outer products
to a question of where to put the transpose is only going to cause *more*
confusion in students, by the way)
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10545#comment:3>
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