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MathGroup Archive 2004

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Re: matrix times a vector

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49045] Re: matrix times a vector
  • From: "Brien Alkire" <brien at rand.org>
  • Date: Tue, 29 Jun 2004 04:50:30 -0400 (EDT)
  • Organization: RAND Corporation
  • References: <cbokn1$4bl$1@smc.vnet.net>
  • Reply-to: "Brien Alkire" <bigtime at majorspam.com>
  • Sender: owner-wri-mathgroup at wolfram.com

Simply transpose the matrix before mulitplying by {x,y}:

Transpose[{{a,b}, {c,d}}]

This extends without change to general nxn matrices.

"David Salomon" <david.salomon at csun.edu> wrote in message
news:cbokn1$4bl$1 at smc.vnet.net...
> Question:
>
> The input {{a,b}, {c,d}}.{x,y} generates the output {a x+b y,c
> x+d y}.
>
> How can I get the output x{a,b}+y{c,d}  ?
>
> This is a special case of lists with two elements. How
> can I extend this computation in an elegant way to lists
> with N elements?
>
> with thanks,
>
>
> |David Salomon
|                                                                         |
> |Computer Science Dept.                     dsalomon at csun.edu        |
> |California State University                http://www.ecs.csun.edu/~dxs
|
> |Northridge, CA 91330-8281                  (818) 677-4954
|
> |USA                                        fax (818) 677-7208
|
> |
|
> |            Macintosh --- because you can see right through windows.
|
>



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