Re: Multiplying a vector over multiple vectors

• To: mathgroup at smc.vnet.net
• Subject: [mg91162] Re: Multiplying a vector over multiple vectors
• From: "David Park" <djmpark at comcast.net>
• Date: Fri, 8 Aug 2008 07:12:59 -0400 (EDT)
• References: <g7ed6u\$2pm\$1@smc.vnet.net>

```testmatrix = {{1, 2}, {3, 4}, {5, 6}};

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

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

--
David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/

"Donald DuBois" <donabc at comcast.net> wrote in message
news:g7ed6u\$2pm\$1 at smc.vnet.net...
> 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
>
> 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).
>