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MathGroup Archive 2004

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Re: [Outer [Times, , ] ] Question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45851] Re: [Outer [Times, , ] ] Question
  • From: drbob at bigfoot.com (Bobby R. Treat)
  • Date: Tue, 27 Jan 2004 04:50:50 -0500 (EST)
  • References: <bv00aa$jda$1@smc.vnet.net> <bv2g3q$6g$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Sorry, it was Ted Ersek's code, not Andzej's. Andrzej had posted a
slightly less complete solution, and I got confused.

Bobby

drbob at bigfoot.com (Bobby R. Treat) wrote in message news:<bv2g3q$6g$1 at smc.vnet.net>...
> MatrixForm objects don't add, because they're not matrices.  But your
> code works perfectly for me, because (see a recent thread on
> MatrixForm), I have installed the following code in my Init.m file
> (thanks to Andrzej Kozlowski):
> 
> Unprotect[MatrixForm];
> HeadTest[func_] := 
>       Intersection[{func}, {If, List, Set, SetDelayed, UpSet,
> UpSetDelayed, \
> TagSet, TagSetDelayed, Format, MakeBoxes, MakeExpression, ToBoxes,
> Shallow, \
> Short, Hold, HoldForm, HoldComplete, HoldPattern, Verbatim, Blank, 
>       BlankSequence,
>  BlankNullSequence, Alternatives, Pattern, Optional, Repeated,
> RepeatedNull,
>       Condition, PatternTest, Rule, RuleDelayed, FullForm, InputForm}]
> === {}
> MatrixForm[MatrixForm[m_]] ^:= MatrixForm[m];
> MatrixForm /: (f_?HeadTest)[
>         a1___, a2_MatrixForm, a3___] := Module[{result}, result =
> Replace[{a1,
>          a2, a3}, MatrixForm -> Identity, 2, Heads -> True];
>     result = f @@ result;
>     If[MatrixQ[result], MatrixForm[result], result]]
> Protect[MatrixForm];
> 
> Bobby
> 
> MichaelSMcCain at cs.com wrote in message news:<bv00aa$jda$1 at smc.vnet.net>...
> > Hi:
> > 
> > I want to take a Column Vector and multiply it by a Row Vector to create an 
> > "Outer" Matrix. 
> > 
> > In other words, I want to take a 5x1 Column Vector and multiply it by a 1x4 
> > Row Vector and output a 5x4 Matrix.
> > 
> > I then want to add several of these Matrices together and obtain a "final" 
> > Matrix.
> > 
> > I tried the following:
> > 
> > x1 = {1, -1, -1, 1, 1};
> > y1 = {1, 1, -1, -1};
> > 
> > x2 = {-1, 1, -1, 1, -1};
> > y2 = {1, -1, 1, -1};
> > 
> > x3 = {1, 1, -1, -1, 1};
> > y3 = {-1, -1, 1, 1};
> > 
> > m1 = MatrixForm[Outer [Times, x1, y1] ]
> > m2 = MatrixForm[Outer [Times, x2, y2] ]
> > m3 = MatrixForm[Outer [Times, x3, y3] ]
> > 
> > mm = m1 + m2 + m3
> > 
> > MatrixForm[mm]
> > 
> > The output that I get is incorrect and does not combine into a single Matrix.
> > 
> > 
> > What am I doing wrong?
> > 
> > Thanks,
> > 
> > 
> > Mike McCain
> > MichaelSMcCain at cs.com


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