[R] plotting prcomp

[Gavin Simpson]

On Fri, 2008-06-27 at 21:43 +0200, Dan Bolser wrote:
> 2008/6/27 Prof Brian Ripley <ripley at stats.ox.ac.uk>:
<snip />
> >
> > I forgot to answer that: just ask R to show you stats:::biplot.prcomp
> 
> Ah! I never knew the ::: trick!

In this case you also need to know that biplot.prcomp is in stats.
getAnywhere() is a more general solution:

getAnywhere(biplot.prcomp)

The following R News article by Uwe Ligges covers aspects of finding the
sources for R functions:

Uwe Ligges. R help desk: Accessing the sources. R News, 6(4):43-45,
October 2006.

HTH

G

> 
> I got it working after looking at the code -
> 
> 
> 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)
> 
> attributes(my.pc)
> 
> head(scores <- my.pc$x)
> 
> lam <- my.pc$sdev
> 
> n <- nrow(my.pc$x)
> 
> lam <- lam * sqrt(n)
> 
> my.x <- (my.pc$x)[,1] / lam[1]
> my.y <- (my.pc$x)[,2] / lam[2]
> 
> plot(my.x, my.y, type="n")
> text(my.x, my.y, labels=1:100)
> 
> 
> 
> >>> 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.
> >>>
> >>>        [[alternative HTML version deleted]]
> >>>
> >>> ______________________________________________
> >>> R-help at 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.
> >>>
> >>
> >> --
> >> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> >> 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,                  ripley at stats.ox.ac.uk
> > 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
> >
> 
> 
> 
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