[R] user coordinates and rug plots in lattice graphics
John Fox
jfox at mcmaster.ca
Mon Apr 8 18:33:35 CEST 2002
Dear Deepayan,
Using current.viewport()$yscale does the trick -- for example:
x <- rnorm(50)
y <- rnorm(50)
f <- factor(sample(c('a','b','c'),size=50, replace=T))
par(tck = 0.03)
z <- xyplot(y~x|f,
panel = function(x,y,...) {
panel.xyplot(x,y,...)
ymin <- current.viewport()$yscale[1]
lpoints(x, rep(ymin, length(x)), pch="|", col='black')
})
z
Thank you very much,
John
At 09:09 AM 4/8/2002 -0700, Deepayan Sarkar wrote:
>--- John Fox <jfox at mcmaster.ca> wrote:
> > Dear R list members,
> >
> > I'd like to produce rug plots at the bottom of panels in a trellis display
> > (using the lattice package), but par("usr") doesn't return user
> coordinates
> > for panels, and consequently rug fails, as the following example
> (suggested
> > to me by Georges Monette) illustrates:
> >
> > > x <- rnorm(50)
> > > y <- rnorm(50)
> > > f <- factor(sample(c('a','b','c'),size=50, replace=T))
> > > z <- xyplot(y~x|f,
> > + panel = function(x,y,...) {
> > + panel.xyplot(x,y,...)
> > + rug(x)
> > + print(par('usr'))
> > + })
> > > z
> > [1] 0 1 0 1
> > [1] 0 1 0 1
> > [1] 0 1 0 1
> > Warning messages:
> > 1: some values will be clipped in: rug(x)
> > 2: some values will be clipped in: rug(x)
> > 3: some values will be clipped in: rug(x)
> >
> > (R Version 1.4.1 on a Windows 2000 PC.)
> >
> > This code runs properly in S-PLUS, by the way, where par("usr") returns
> > user coordinates when invoked within a panel function.
>
>The problem arises because lattice is based on grid graphics, and conventional
>R graphics do not work under grid. The way around (to get the user
>coordinates) here would be to use current.viewport()$xscale and
>current.viewport()$yscale (both should be vectors of length 2).
>
> > I don't see a way around the problem. If I could determine the minimum
> > value of y in a panel, I could make my own rug plot. Any help would be
> > greatly appreciated.
>
>For this, you might want to use lsegments. (This may be slow now, but should
>be faster in the next release.)
-----------------------------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox
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