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Re: solving equation system

From: Eric Chassande-Mottin
Subject: Re: solving equation system
Date: Tue, 19 Apr 2005 13:14:10 -0500

> I hope that someone can point out a shorter way to define the coefficient
> matrix since all its rows are of the form [1,x,x^2,x^3,x^4].

here, a is a vandermonde matrix

a=vander([124.5 111 88.9 75.5 63]);

octave:1> a=vander([124.5 111 88.9 75.5 63])
a =

   2.4026e+08   1.9298e+06   1.5500e+04   1.2450e+02   1.0000e+00
   1.5181e+08   1.3676e+06   1.2321e+04   1.1100e+02   1.0000e+00
   6.2461e+07   7.0260e+05   7.9032e+03   8.8900e+01   1.0000e+00
   3.2493e+07   4.3037e+05   5.7002e+03   7.5500e+01   1.0000e+00
   1.5753e+07   2.5005e+05   3.9690e+03   6.3000e+01   1.0000e+00

you need to flip it to choose the same coordinate system as you did:


> octave:6>
> a=[1,124.5,124.5^2,124.5^3,124.5^4;1,111,111^2,111^3,111^4;1,88.9,88.9^2,88.9^3,88.9^4;1,75.5,75.5^2,75.5^3,75.5^4;1,63,63^2,63^3,63^4]
> a =
>    1.0000e+00   1.2450e+02   1.5500e+04   1.9298e+06   2.4026e+08
>    1.0000e+00   1.1100e+02   1.2321e+04   1.3676e+06   1.5181e+08
>    1.0000e+00   8.8900e+01   7.9032e+03   7.0260e+05   6.2461e+07
>    1.0000e+00   7.5500e+01   5.7002e+03   4.3037e+05   3.2493e+07
>    1.0000e+00   6.3000e+01   3.9690e+03   2.5005e+05   1.5753e+07


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