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MathGroup Archive 2005

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Re: MatrixForm

  • To: mathgroup at smc.vnet.net
  • Subject: [mg62574] Re: [mg62567] MatrixForm
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Tue, 29 Nov 2005 04:44:04 -0500 (EST)
  • References: <200511280557.AAA18494@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 28 Nov 2005, at 14:57, David Park wrote:

> Sometimes MatrixForm seems annoying because it is not transparent  
> to other operations as some of the other Forms are. Actually, I  
> think its design is very good because it allows one to write matrix  
> equations with the Dot product in a nice form, and then easily  
> evaluate them.
>
> A = Array[a, {2, 2}];
> B = Array[b, {2, 2}];
>
> 3 MatrixForm[A].MatrixForm[B]
> % /. MatrixForm -> Identity // MatrixForm
>
> The Dot product won't evaluate when the matrices are wrapped in  
> MatrixForm and so we get the regular textbook form of a product.  
> Notice also that the factor 3 was not sucked into the matrices.  
> Using the rule  MatrixForm -> Identity then evaluates the matrix  
> multiplication.
>
> I don't know how many users are aware of this usage. I have just  
> begun to appreciate it and thought I would post a note on it.
>
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
>


This is all true but... if you replace MatrixForm with  
TraditionalForm in the above you will get all the advantages  
described plus a little nicer output. And, if your Default Output  
Format type is set to TraditionalForm you won't need the last // 
TraditionalForm.

Is there any point in keeping MatrixForm other than compatibility  
with earlier versions of Mathematica?

Andrzej Kozlowski


  • References:
    • MatrixForm
      • From: "David Park" <djmp@earthlink.net>
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