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Re: How to do symbolic matrix manipulations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92295] Re: How to do symbolic matrix manipulations
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sat, 27 Sep 2008 06:48:06 -0400 (EDT)

On 9/26/08 at 6:23 AM, pengyu.ut at gmail.com (Peng Yu) wrote:

>Suppose I have matrices a and b, which does not have any value yet.

>If I write b * a, mathematica would give me "a b". I'm wondering how
>to make it know that a and b are matrices, so that it would give me
>"b a" rather than "a b".

The key here is to realize b*a will always commute including
when both a,b are matrices since this does an element by element
multiplication not a matrix multiplication. Simply do matrix
multiplication using Dot and there is no problem. That is

In[1]:= b.a

Out[1]= b.a


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