[R] eigen vector sign reversal

Martin Maechler maechler at stat.math.ethz.ch
Wed Jul 16 09:21:56 CEST 2003

>>>>> "Roger" == Roger D Peng <rpeng at stat.ucla.edu>
>>>>>     on Tue, 15 Jul 2003 10:19:38 -0700 writes:

    Roger> I think at version 1.7.0 R started using LAPACK for
    Roger> its eigen/svd routines.  I think using `eigen(x,
    Roger> EISPACK = TRUE)' uses the previous version.

Yes (2 x).

But it the eigen vectors *are* determined only upto
multiplication with +/- 1.
So I think Karim should consider improving the R scripts that 
have been dependent on particular signs of the eigen vectors.

    Roger> Karim Elsawy wrote:

    >> I've just installed R 1.7.1 under linux red hat I noticed
    >> sign reversal of eigen vectors ,some of them not all,
    >> upon using diag function relative to those obtained using
    >> R 1.4.1 this is gonna miss up lots of my previous scripts
    >> I wonder if there is a way to avoid this.  best regards
    >> karim

Martin Maechler <maechler at stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum  LEO C16	Leonhardstr. 27
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1228			<><

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