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