Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: How to do symbolic matrix manipulations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92298] Re: How to do symbolic matrix manipulations
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 27 Sep 2008 06:48:40 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <gbjmam$3ab$1@smc.vnet.net>

Peng Yu wrote:

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

Beware that Mathematica is not a strongly-type language and things like 
vector or matrix do not exist per se. A vector can be represented by a 
one dimensional list holding appropriate element, a matrix by a two 
dimensional list; but a generic type vector or matrix does not exist 
natively.

> 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".

You could use the non-commutative multiplication operator **.

In[213]:= b ** a

Out[213]= b ** a

If you are going to do extensive symbolic manipulation withe generic 
objects, you may want to define your own matrix type (say expression 
with head matrix, i.g. something like matrix[a]) and 
associate/(re)define properties and operator.

Regards,
-- Jean-Marc


  • Prev by Date: Re: Help
  • Next by Date: SparseArray
  • Previous by thread: Re: How to do symbolic matrix manipulations
  • Next by thread: flop-count