[R] Lattice dotplot with symbols sized and colored

[Sundar Dorai-Raj]

David Kidd wrote on 5/3/2005 3:08 AM:
> 
> Apologies if this is a naive beginners question.
> 
> I am trying to create a dotplot with the lattice dotplot function in 
> which my dots are colored differently depending on if positive or 
> negative and sized by sp.nc.bdrs.data$mwZ
> 
> I have tried...
> 
> dotplot(sporder ~ cvarorder | direct, data=sp.nc.bdrs.data,
> cex=abs(sp.nc.bdrs.data$mwZ * 0.05),
> xlab="climate variables",
> ylab="species",col= sp.nc.bdrs.data$mysign,
> scales = list(y = list(labels = as.character(spname),at = 1:12, cex = 
> 0.5), x = list(labels = as.character(my.ylabel), at = 1:66, rot=90, cex 
> = 0.5), alternating = 3))
> 
> This sizes my symbols correctly but colors all four conditional plots 
> (direct = 'e', 'n', 's' & 'w') using the colors defined for the first 
> direct condition (i.e. 'e').
> 
> I have also tried using 'groups' to set the colors, however, whenever I 
> do this I cannot get cex to then size the symbols - I get open circles 
> that do not scale. This problem also happens when I try setting up a 
> panel function.
> 
> Many Thanks
> 
> 
> 
> 

Hi David,

I think you're on the right track using groups. However, you just have 
to set the trellis arguments correctly. For example,

library(lattice)
my.theme <- function() {
   theme <- col.whitebg()
   symb <- theme$superpose.symbol
   symb$cex <- seq(0.5, 1.5, length = length(symb$cex))
   # symb$pch is c(1, 3, 6, 0, 5, 16, 17) by default for col.whitebg
   theme$superpose.symbol <- symb
   theme
}
trellis.par.set(theme = my.theme())
# from ?dotplot
dotplot(variety ~ yield | year, data = barley, groups = site)

It's not necessary to create a theme. You can accomplish the same just 
using trellis.par.get and trellis.par.set. The above is just my personal 
preference.

HTH,

--sundar