[R] Adding points on top of lines in xyplot

[Dylan Beaudette]

On Tuesday 20 November 2007, Deepayan Sarkar wrote:
> On 11/20/07, Dylan Beaudette <debeaudette at ucdavis.edu> wrote:
> > On Tuesday 20 November 2007, Deepayan Sarkar wrote:
> > > On Nov 20, 2007 11:14 AM, David Afshartous <dafshartous at med.miami.edu>
> >
> > wrote:
> > > > All,
> > > >
> > > > I'm trying to make a basic plot: data points superimposed upon the a
> > > > line connecting the points w/ a different color.  Example below
> > > > doesn't work as the first xyplot call doesn't remain.  Suggestions?
> > >
> > > xyplot(y ~ Hour, type = 'b', lwd = 2, pch= 16, col.symbol =  "red",
> > > cex=3)
> > >
> > > or for finer control
> > >
> > > xyplot(y ~ Hour,
> > >        panel = function(x, y, ...) {
> > >            panel.lines(x, y, lwd = 2)
> > >            panel.points(x, y, pch = 16, cex = 3, col = "red")
> > >        })
> > >
> > > -Deepayan
> >
> > Deepayan,
> >
> > is there any way to do something similar, but when the data used to plot
> > the lines and the points come from different dataframes and a grouping
> > variable is used?
>
> There's a way to do almost everything, but we need a reproducible
> example (preferably minimal) and a clear statement of what you want to
> do to help.
>
> -Deepayan


Of course! Sorry about that. 

Example:
library(lattice)

# generate some data:
resp <- rnorm(100)
pred <- resp*1.5 + rnorm(100)
d <- data.frame(resp=resp, pred=pred)

# add a grouping factor:
d$grp <- gl(4, 25, labels=letters[1:4])

# plot: looks ok!
main.plot <- xyplot(resp ~ pred | grp, data=d, panel=function(x,y, ...) 
{panel.xyplot(x, y, ...) ; panel.lmline(x,y, ...) })

# however, we have some other information which needs to go in each panel
# note that the dimensions (i.e. no of obs) are not the same as the original 
# data, and the values are different, but on the same scale
resp.other <- rnorm(20)
pred.other <- resp.other*1.5 + rnorm(20)
d.other <- data.frame(resp=resp.other, pred=pred.other)
d.other$grp <- gl(4, 5, labels=letters[1:4])


The big question:
Now that we have the main plot (main.plot) looking ok, how can we add the data 
from d.other to the frames of main.plot without using subset() for each level 
of our grouping variable?


# after some messing around, how about this:
xyplot(resp ~ pred | grp, data=d, panel=function(x,y, ...)
{
panel.xyplot(x, y, ...) 
panel.lmline(x,y, ...) 
# now the other data:
panel.superpose(d.other$pred, d.other$resp, groups=d.other$grp, 
col=c('red', 'blue', 'green', 'orange')[as.numeric(d.other$grp)], pch=16, 
subscripts=TRUE)
}
)

#... hmm it doesn't look like the information from 'd.other' is being 
stratified into the panels setup in panel.xyplot() ... 

The main point to this rather contrived example is this : 

1. i have a data frame with continuous predictions, the response, and the 
grouping variable -- which plot nicely with the default use of xyplot()

2. I would like to embellish each panel with the original response and 
predictor values to illustrate the relationship between the original data and 
the smooth, fitted curve.

ideas?

thanks!

Dylan


-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341