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Re: Dot Product of Vectors

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89075] Re: [mg89044] Dot Product of Vectors
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Sun, 25 May 2008 03:21:16 -0400 (EDT)
  • References: <200805240755.DAA20910@smc.vnet.net>

On 24 May 2008, at 16:55, Gregory Lypny wrote:

> Hello everyone,
>
> I've got two n x k matrices called X and Y.  I'd like to compute an n
> x 1 vector whose elements are the dot products of corresponding rows
> of X and Y, that is,
>
> 	{{X[[1]].Y[[1]]}, {X[[2]].Y[[2]]}, {X[[3]].Y[[3]]}, ...
> {X[[n]].Y[[n]]}.
>
> I found that this can be done using MapThread as
>
> 	MapThread[Dot, { X, Y}],
>
> which is straightforward.  I'm curious, given that there a zillion
> ways to do any given calculation in Mathematica, if anyone knows of
> another way that is as compact.
>
> Regards,
>
> 	Gregory
>
>
>


Total[X*Y, {2}]

Andrzej Kozlowski


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