Re: Can't multiply non-square matrices.
- To: mathgroup at smc.vnet.net
- Subject: [mg64622] Re: Can't multiply non-square matrices.
- From: bghiggins at ucdavis.edu
- Date: Fri, 24 Feb 2006 00:18:18 -0500 (EST)
- References: <dthgr4$n74$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Chris,
A matrice defined in a typical Linear algebra textbook is in terms of
rows and columns. Thus a 3-row by 2-column matrix times a 2-row by
1-column matrix yields a 3-row by 1-column matrix. In Mathematica this
is done as follows:
Here is my 3-row by 2-column matrix:
mat32={{a1, b1}, {a2, b2}, {a3, b3}}
Here is my 2-row by 1-column matrix:
mat21={c1, c2}
And the multiplication is then:
mat32.mat21
{a1 c1 + b1 c2, a2 c1 + b2 c2, a3 c1 + b3 c2}
which is a 3-row by 1-column matrix.
Note a row vector and column vector (as defined in Linear algebra
texts) are treated the same in Mathematica.
Cheers,
Brian