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Re: Multiplying a vector over multiple vectors

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91160] Re: [mg91150] Multiplying a vector over multiple vectors
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 8 Aug 2008 07:12:37 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

Map[{a, b} # &, {{1, 2}, {3, 4}, {5, 6}}]

{{a, 2*b}, {3*a, 4*b}, {5*a, 6*b}}

{a, b} # & /@ {{1, 2}, {3, 4}, {5, 6}}

{{a, 2*b}, {3*a, 4*b}, {5*a, 6*b}}


Bob Hanlon

---- Donald DuBois <donabc at comcast.net> 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




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