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MathGroup Archive 2006

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Re: Matrix Multiplication (with a twist)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68984] Re: [mg68951] Matrix Multiplication (with a twist)
  • From: Adriano Pascoletti <pascolet at dimi.uniud.it>
  • Date: Sat, 26 Aug 2006 02:04:19 -0400 (EDT)
  • References: <200608250935.FAA09217@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 25 ago 2006, at 11:35, Bruce Colletti wrote:

> For matrix A = {{e,f},{g,h}} and B = {{a,b},{c,d}}, Mathematica  
> returns their product
>
> A.B = {{ae+cf,be+df},{ag+ch,bg+dh}}
>
> However, I want to treat multiplication of numeric variables as  
> noncommutative in order to instead obtain the result
>
> {{ea+fc, eb+fd},{ga+hc,gb+hd}}
>
> How would this be done in v5.2?  Thanks.
>
> Bruce
>

In[1]:=
A = {{e,f},{g,h}} ; B = {{a,b},{c,d}};
Inner[NonCommutativeMultiply, A, B, Plus]

Out[2]=
{{e**a+f**c,e**b+f**d},{g**a+h**c,g**b+h**d}}

Adriano Pascoletti


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