From: Angel Lopez <angel_lul_at_hotmail.com>

Date: Thu 01 Jul 2004 - 04:37:01 EST

R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 01 04:45:21 2004

Date: Thu 01 Jul 2004 - 04:37:01 EST

Thanks for the pointers.

I've read them with care but I don't seem capable of making it work.
For example, if I do:

data(USArrests)

USArrests2<-USArrests

USArrests2[1,1]<-NA

princomp(USArrests2, cor = TRUE, na.action = "na.omit")

I get the error message:

Error in cov.wt(z) : x must contain finite values only

I've tried changing the 'options' na.action and using other values than na.omit with no success.

The only way that I can make it work in some way was if I did:

USArrestsNA<-na.omit(USArrests)

princomp(USArrestsNA, cor = TRUE)

I've also obtained the same by giving the correlation matrix instead of
the data frame:

princomp(covmat=cor(USArrestsNA))

Both solutions do the job by not using the row with the NA.
After more reading I thought I would get the same result by doing:
princomp(covmat=cor(USArrests2,use="complete.obs"))
but the result is slightly different. I can not manage to understand the
difference.

Can someone give me some more light to keep going?
P.S:Using the solution above with na.omit would not be very good in my
real world problem because it is relatively common to have an NA in a
row. Maybe using

princomp(covmat=cor(USArrests2,use="pairwise.complete.obs"))
would be a solution but I would like to understand the above before
doing this next step.

Thanks,

Ange

Prof Brian Ripley wrote:

*> On Wed, 30 Jun 2004, Angel Lopez wrote:
**>
**>
**>>I need to perform a principal components analysis on a matrix with
**>>missing values.
**>>I've searched the R web site but didn't manage to find anything.
**>
**>
**> ?princomp
**>
**> has a description of an na.action argument, and
**>
**> help.search("missing values")
**>
**> comes up with several relevant entries.
**>
*

R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Jul 01 04:45:21 2004

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