| To: | Abderrahim Oulhaj <abderrahim.oulhaj@pharmacology.oxford.ac.uk>, s-news@lists.biostat.wustl.edu |
|---|---|
| Subject: | Re: solve |
| From: | "Richard M. Heiberger" <rmh@temple.edu> |
| Date: | Tue, 14 Dec 2004 14:02:32 -0500 |
Your example is very badly conditioned
A <- matrix(c(613537.28025, -49.536866569,-49.53687, 0.004000337),nrow = 2,
byrow=TRUE)
> eigen(A)
$values:
[1] 6.135373e+005 7.408900e-007
$vectors:
[,1] [,2]
[1,] 0.99999999674 0.00008073978
[2,] -0.00008073979 0.99999999674
>
The ratio of eigenvalues is 10^12.
S-Plus solve is using a tolerance of 1e-7 (in qr.default)
R solve is using a tolerance of 2e-16 (in solve.default)
Rich
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