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Can't multiply non-square matrices.

• To: mathgroup at smc.vnet.net
• Subject: [mg64549] Can't multiply non-square matrices.
• From: Chris Young <c1572young at earthlink.net>
• Date: Wed, 22 Feb 2006 05:58:31 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Is there a way to multiply non-square matrices? E.g., a 3-row by 2-row 
matrix times a 2-row by 1-row matrix should yield a 3-row by 1-row 
matrix, if I remember my linear algebra correctly.

Instead when I do something like

   (a  b) (c)
          (d)

I get an error involving "Thread::tdlen":

Thread::tdlen: Objects of unequal length in {{a, b}}\{{c}, {d}} cannot be \
combined.

(The "(c)" and "(d)" above represent a 2-dimensional column vector, 
with one pair of parenthese around them.)

I entered the line
<< LinearAlgebra`MatrixManipulation`
but this doesn't seem to help.

Any help appreciated.

Chris Young

• Follow-Ups:
  • Re: Can't multiply non-square matrices.
    • From: "Yasvir A. Tesiram" <tesiramy@omrf.ouhsc.edu>