Re: column * row ??

• To: mathgroup at smc.vnet.net
• Subject: [mg28819] Re: column * row ??
• From: "Allan Hayes" <hay at haystack.demon.co.uk>
• Date: Tue, 15 May 2001 00:58:54 -0400 (EDT)
• References: <9dlcc6\$o2p@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```John,
We need to make the lists into matrice -- column and row matrices:

{{a1},{a2},{a3}}.{{b1,b2}}

{{a1 b1,a1 b2},{a2 b1,a2 b2},{a3 b1,a3 b2}}

--
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

"J.R. Chaffer" <jrchaff at mcn.net> wrote in message
news:9dlcc6\$o2p at smc.vnet.net...
> Hi there,
>
> Can someone tell me a way to mimic the building of
> an N x N matrix by multiplying a column vector
> on left times a row vector on right ? (both vectors
> of length N) - I mean in Mathematica, of course.
>
> i.e, want the result,
>
> (colvec){a1,a2, .. aN} * (rowvec){b1,b2,..bN} =
>
> result is matrix:
>
> {{a1*b1  a1*b2 .....  a1*bN},
>  {a2*b1  a2*b2 .....  a2*bN},
>   ...     ...          ...  ,
>  {aN*b1  aN*b2 .....  aN*bN}}
>
>
> When I try this in Mathematica all I can figure out
> how to produce is the standard dot-product.  If I
> try the 'transposed' lists/matrices, I get an error,
> even tho the product is defined by basic rules of
> matrix multiplication.
>
> Thanks,
>
> John Chaffer
>

```

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