       Re: [Outer [Times, , ] ] Question

• To: mathgroup at smc.vnet.net
• Subject: [mg45834] Re: [Outer [Times, , ] ] Question
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Tue, 27 Jan 2004 04:50:28 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <bv00aa\$jda\$1@smc.vnet.net>
• Reply-to: kuska at informatik.uni-leipzig.de
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

remove the MatrixForm[], MatrixForm[] is
a format function that wrap around your expression
and hinder Plus[] to work
as expected.

Regards
Jens

MichaelSMcCain at cs.com wrote:
>
> Hi:
>
> I want to take a Column Vector and multiply it by a Row Vector to create an
> "Outer" Matrix.
>
> In other words, I want to take a 5x1 Column Vector and multiply it by a 1x4
> Row Vector and output a 5x4 Matrix.
>
> I then want to add several of these Matrices together and obtain a "final"
> Matrix.
>
> I tried the following:
>
> x1 = {1, -1, -1, 1, 1};
> y1 = {1, 1, -1, -1};
>
> x2 = {-1, 1, -1, 1, -1};
> y2 = {1, -1, 1, -1};
>
> x3 = {1, 1, -1, -1, 1};
> y3 = {-1, -1, 1, 1};
>
> m1 = MatrixForm[Outer [Times, x1, y1] ]
> m2 = MatrixForm[Outer [Times, x2, y2] ]
> m3 = MatrixForm[Outer [Times, x3, y3] ]
>
> mm = m1 + m2 + m3
>
> MatrixForm[mm]
>
> The output that I get is incorrect and does not combine into a single Matrix.
>
> What am I doing wrong?
>
> Thanks,
>
> Mike McCain
> MichaelSMcCain at cs.com

```

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