[GRASS-stats] Re: [GRASS-user] Testing i.pca ~ prcomp(), m.eigensystem ~ princomp()

[Nikos Alexandris]

Nikos:
> > If outputs are not identical, either R or grass do some hidden
> > modification or there is a bug in either grass or R (all within
> > limits, e.g. identical up to the 5th digit in scientific format is
> > fine?).
> > Some textbooks give a rule of thumb for further analysis to use only
> > components with an eigenvalue >=1

> I think this depends on what you are trying to achieve. Of course,
> components with small(-er) eigenvalues include more "noizzze". In my
> change detection project I used *only* components with eigenvalues <
> 1.

Hmm.. Markus, I was too quick yesterday. That's not true. All of the
PC's I've used have "eigenvalue > 1". Sorry :-p