R help - May 2001 - Screeplot

I'm trying to make a screeplot including the Cumulative Proportion of
the Variance, something that can easily be done in S-Plus with
'screeplot(pc.object,cumulative=T)'. How can I access the Proportion of
Variance in an princomp object and how could I get the Cumulative
Proportion of the Variance on the screeplot?

Many thanks in advance, Jan:-)


-- 
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 Jan Kleinn                                   tel: +41-1-635 52 34
 Institute for Climate Research ETH           fax: +41-1-362 51 97
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Jan Kleinn wrote:
> I'm trying to make a screeplot including the Cumulative Proportion of
> the Variance, something that can easily be done in S-Plus with
> 'screeplot(pc.object,cumulative=T)'. How can I access the
Proportion of
> Variance in an princomp object and how could I get the Cumulative
> Proportion of the Variance on the screeplot?
>From start to screeplot:
library(mva)
mydata <- mvrnorm(300, rep(0, 4), diag(4))
my.pcomp <- princomp(mydata)
y <- my.pcomp$sdev^2
cpropvar <- cumsum(my.pcomp$sdev^2 / sum(my.pcomp$sdev^2))
x <- barplot(y, col=rep(1, dim(mydata)[2]), ylim=c(0, 6))
text(x, y + 0.25, round(cpropvar, 2), adj=0.5)

To suit your data, you would need to play with the ylim parameters and the
distance of the cumulative proportion of variance labels from the tops of the
bars.

HTH,

Chuck
 
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 Chuck Cleland                                 
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