[R] dotplot (lattice) with panel.segments and groups

[Sebastian Luque]

Hi,

The following produces almost exactly what I needed.  The problems are
that the 'panel.dotplot' call (commented) generates the error 'Error in
NextMethod("[") : argument "subscripts" is missing, with no default'.  The
other problem is that the colors alternate between the levels of the 'site'
variable, rather than 'year'.


barley$yield2 <- with(barley, yield + 5)

dotplot(site ~ yield | variety, data=barley, groups=year,
        yield2=barley$yield2, col=c("gray", "black"),
        panel=function(x, y, subscripts, yield2, ...) {
            ## panel.dotplot(x, y, ...)
            panel.segments(x, as.numeric(y),
                           yield2[subscripts], as.numeric(y), ...)
        })

R> sessionInfo()
Version 2.3.1 (2006-06-01) 
i486-pc-linux-gnu 

attached base packages:
[1] "methods"   "stats"     "graphics"  "grDevices" "utils"     "datasets" 
[7] "base"     

other attached packages:
   chron  gmodels  lattice 
 "2.3-3" "2.12.0" "0.13-8"


Can somebody please suggest how to properly make that 'panel.dotplot' call
and set the 'col' argument?  Thanks in advance.


Cheers,

-- 
Seb