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MathGroup Archive 1999

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Re: Don't want to calculate scalar product

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19721] Re: Don't want to calculate scalar product
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Mon, 13 Sep 1999 02:40:55 -0400
  • References: <7ree45$489@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Toshiyuki (Toshi) Meshii <meshii at mech.fukui-u.ac.jp> wrote in message
news:7ree45$489 at smc.vnet.net...
> Hi,
>
> I understand that one of the unique point of Mathematica is that you don't
> have to be conscious about whether a vector is a "row" or a "column"
vector.
>
> However, I think there is a case in which you have to specify whether you
> want Mathematica to recognize a vector as a row vector or a column vector.
> Let me explain my case.
>
> a={1,2,3}; b={4,5,6}
>
> I want to define "a" as a column vector (3x1 matrix) and "b" as a row
vector
> (1x3 matrix).
>
> I expect the product
>  a.b
> as a 3x3 matrix, but the answer Mathematica gives is a scalar product
"32".
>
> Please give me an advice to get the 3x3 matrix as a product.
>
> -Toshi
>

Toshi,
Make a into a 1x3 matrix an b into a 3x1 matrix :

a = {1, 2, 3}; b = {4, 5, 6};


List /@ a  .{b}

{{4, 5, 6}, {8, 10, 12}, {12, 15, 18}}


--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565




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