       Re: Don't want to calculate scalar product

• To: mathgroup at smc.vnet.net
• Subject: [mg19739] Re: Don't want to calculate scalar product
• From: phbrf at t-online.de (Peter Breitfeld)
• Date: Mon, 13 Sep 1999 02:41:04 -0400
• Organization: das ist ein breites Feld ...
• References: <7ree45\$489@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Toshiyuki (Toshi) Meshii <meshii at mech.fukui-u.ac.jp> schrieb:
> 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".
>
Mathematica doesn't distiguish between row and column vectors. You have
to use Outer:

In:=Outer[Times, a, b]
Out={{4, 5, 6}, {8, 10, 12}, {12, 15, 18}}

Peter
--
=--=--=--=--=--=--=--=--=--=--=--=--=  http://home.t-online.de/home/phbrf  =--=
=--= Peter Breitfeld, Saulgau, Germany        PGP public key: 08548045  =--=--=

```

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