R help - Jul 2011 - Package rrcov, functions PcaCov, PcaHubert, PcaGrid

Hello,

I'm using the R-2.13.1 version in Windows and I'm trying to do a robust
Pca
with the following:

x<-matrix(0.5,30,30)
library("rrcov")

y<-PcaCov(x)

The following error occurs: 
Error: diff(sv)<0 ist not all TRUE

The same error occurs with the other functions. What does this mean and how
can I perform the robust PCA with these functions by using a quadratic
matrix as input?

Thanks in advance,
Albina.

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On Jul 13, 2011; 12:03pm Albina wrote:
> Error: diff(sv)<0 ist not all TRUE
> ... . >snip<
> The same error occurs with the other functions. What does this mean and
> how can I perform the robust 
> PCA with these functions by using a quadratic matrix as input?
Albina,

You at least need to feed it something sensible. Look at your matrix:

x<-matrix(0.5,30,30)
x

Try the following:
x <- rmultinom(30, size = 30, prob=rep(c(0.1,0.2,0.8), 30))
PcaCov(x)

Regards, Mark.

-----
Mark Difford (Ph.D.)
Research Associate
Botany Department
Nelson Mandela Metropolitan University
Port Elizabeth, South Africa
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Ok, thank you Mark.

I also found out, that it is not a good idea to perform a Pca with the equal
numbers of observation and variables. It is preferable to have much more
observations.

Regards, 
Albina.

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