       Re: Matrices with Mathematica 5.1

• To: mathgroup at smc.vnet.net
• Subject: [mg63333] Re: [mg63315] Matrices with Mathematica 5.1
• From: gardyloo at mail.wsu.edu
• Date: Sat, 24 Dec 2005 07:18:58 -0500 (EST)
• References: <200512231008.FAA25936@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```  Hi,

I'd try extracting the last column and then using LinearSolve on it:

m = {{1, 7, -2, 0, 8, -3}, {0, 0, 1, 1, 6, 5},
{0, 0, 0, 1, 3, 9}, {0, 0, 0, 0, 0, 0}};

Needs["Statistics`DataManipulation`"]

In:=
Column[m, -1]

Out=
{-3, 5, 9, 0}

In:=
s = Module[{}, v = Column[m, -1]; LinearSolve[m, v]]

Out=
{-11, 0, -4, 9, 0, 0}

In:=
m . s == v

Out=
True

In:=
\$Version

Out=
5.2 for Linux (June 20, 2005)

Good luck,
C.O.

> I would like to solve the system given by:
>
> [1  7  -2  0  -8  -3]
> [0  0  1  1    6   5]
> [0  0  0  1    3   9]
> [0  0  0  0    0   0]
>
> Where the matrix is a typical matrix in the form x1+x2+...+xn = b where
> b is the last item in the row.  For example, row 1 could be written as
> x1 + 7x2 - 2x3 -8x4 = -3.  How could I get mathematica to solve this
> matrix?  I understand how to build a matrix, I just need to know the
> operation to run on it.  I tried to use LinearSolve but I did something
> wrong.  Is there a built-in operation to solve these matrices?  If so,