Re: [Outer [Times, , ] ] Question

• To: mathgroup at smc.vnet.net
• Subject: [mg45855] Re: [Outer [Times, , ] ] Question
• From: Mariusz Jankowski<mjankowski at usm.maine.edu>
• Date: Tue, 27 Jan 2004 04:51:01 -0500 (EST)
• Organization: University of Southern Maine
• References: <bv00aa\$jda\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Remove MatrixForm from your lines m1 = ..., m2 = ... etc

Mariusz

>>> <MichaelSMcCain at cs.com> 1/25/2004 3:55:38 AM >>>
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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