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Re: Multiplying a vector over multiple vectors

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91179] Re: [mg91150] Multiplying a vector over multiple vectors
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Fri, 8 Aug 2008 07:16:23 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200808070842.EAA02140@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

   First /@ Outer[Times, {{1, 2}, {3, 4}, {5, 6}}, {{a, b}}, 1]
{{a,2 b},{3 a,4 b},{5 a,6 b}}

Donald DuBois wrote:
> How does one get a vector to distribute over
> a list of vectors  under multiplication?
> 
> For example:
> 
>  {{1,2}, {3,4}, {5,6}} times {a,b} should
> equal  (under this operation)
> 
> {{a, 2b}, {3a, 4b}, {5a, 6b}}
> 
> If {a,b} is duplicated three times one can
> use MapThread as in: 
> 
> MapThread[Times, {{{1, 2}, {3, 4}, {5, 6}}, {{a, b}, {a, b}, {a, b}}}]
> 
> but duplicating {a,b} using Table is very slow
> when the vectors are large (consisting of thousands
> of elemets).
> 
> Thanks in advance for any help you can give me.
> 
> Don
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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