On Fri, 27 Jun 2008, Prof Brian Ripley wrote:
On Fri, 27 Jun 2008, Dan Bolser wrote:
Please consider the following PCA example;
my.df <-
data.frame(A=(x <- rnorm(100,mean=100, sd=10)),
B=(y <- x + rnorm(100,mean=10, sd=10)))
plot(my.df)
my.pc <-
prcomp(my.df, center=TRUE, scale=TRUE)
biplot(my.pc)
my.x <- (my.pc$x)[,1]
my.y <- (my.pc$x)[,2]
plot(my.x, my.y, type="n")
text(my.x, my.y, labels=1:100)
Clearly the plots have the same relative values, but I can't work out how
the second plot is relative to the first. I have been reading the manual,
but I still can't work it out.
Can anyone show me the code to generate the data that I see plotted using
biplot?
I forgot to answer that: just ask R to show you stats:::biplot.prcomp
What am I missing?
Reading the references on ?biplot.prcomp, or a good book on the subject (such
as MASS or Gower & Hand).
A biplot is a specific type of plot and the help page does not spell out the
rather mathematical details (and there are several variants).
Dan.
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--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
