Grass/Erdas PCA

[Agustin Lobo]

> From grass-lists-owner at max.cecer.army.mil Wed Apr 21 07:29:25 1993
> Date: Wed, 21 Apr 1993 08:51:09 -0500
> From: Anantha Prasad <prasad at ghat.inhs.uiuc.edu>
> Sender: lists-owner at max.cecer.army.mil
> Reply-To: grassu-list at max.cecer.army.mil
> To: grassu-list at max.cecer.army.mil
> Subject: Grass/Erdas PCA
> Content-Length: 492
> 
> Hi Grass/Erdas Users:
> Is anybody in this group aware of the fact that the covariance matrix calculated by r.covar (and hence the eigenvalues/vectors and Principal Components calculated by Grass) is quite different from the results obtained by using PRINCE in Erdas? (When it is run on identical sets of maps). What could be the reason for this? Is there some bug? I have tried with different options but still the problem remains. Thanks. Prasad (prasad at ghat.inhs.uiuc.edu  Ph: 217-244-2166)
> 

I did communicate to the list and to bug.report a simmilar problem in March. I'm
looking into this problem. My advice is that you should use m.eigensystem instead of r.pca. I'm not aware of any problem with r.covar, though. I will look into this asap, it's a critic question to me.
Agus