[R] Apparent different in symbol scaling between xyplot and grid.points

[baptiste auguie]

Hi,

I think the size mismatch occurs because of a different default for
the fontsize (and grid.points has a size of 1 character by default).
Compare the following two examples,

# default
grid.newpage()
pushViewport(viewport(x=unit(0.5, "npc"), y=unit(0.5, "npc")))
lplot.xy(data.frame(x=0.55,y=0.5),type="p", pch=3)
grid.points(x=0.45,y=0.5, pch=3, gp=gpar(col="red"))


trellis.par.set("fontsize", list(points=12))

grid.newpage()
pushViewport(viewport(x=unit(0.5, "npc"), y=unit(0.5, "npc")))
lplot.xy(data.frame(x=0.55,y=0.5),type="p", pch=3)
grid.points(x=0.45,y=0.5, pch=3, gp=gpar(col="red"))

HTH,

baptiste

2009/12/4 Sebastien Bihorel <Sebastien.Bihorel at cognigencorp.com>:
> Dear R-users,
>
> For the past few days, I have been trying to find the reason why some of my
> plots were showing symbols of different sizes, while I thought I was using
> the same .cex arguments everywhere. The problem is exemplified by the
> following example code where the xyplot and grid.points functions are used.
> The scaling factor is set to 0.84 in both the functions settings, but one
> can see that, in the pdf file, the blue symbols plotted by xyplot are
> smaller than the single black symbol created by grid.points. Playing with
> the trellis settings did not seem to solve the problem. I am missing a
> hidden scaling factor somewhere, but don't know where to look anymore
>
> I would greatly appreciate the feedback of the list on this issue.
>
> library(lattice)
> library(grid)
>
> pdf(file="test.pdf")
>
> df <- data.frame(a=1:12,b=1:12,c=rep(1:4,each=3))
>
> #trellis.par.set(superpose.symbol=list(cex=1))
>
> xyplot(b~a|c,
>      data=df,
>      panel = function(x,y){
>        panel.xyplot(x,y,pch=3,cex=0.84)}
>      )
>
> str(trellis.par.get())      str(get.gpar())
> grid.points(x=100,y=85,pch=3,gp=gpar(cex=0.84))
>
> dev.off()
>
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