[R] panel.levelplot() for 2D histograms

[Deepayan Sarkar]

On 2/6/06, Vermeiren, Hans [VRCBE] <hvermei1 at vrcbe.jnj.com> wrote:
> Dear R-wizards,
> I'm trying to plot "binned scatterplots", or 2d histograms, if you wish, for
> a number of groups by using the lattice functionality
> it works fine for one group at a time, and probably I could find a
> work-around, but I prefer to do it the elegant way
> here's an example of what I want, what I tried and where it goes wrong:

If you are doing this for fun, read on. Otherwise, I suggest that you
look at the hexbin package (available from bioconductor) for a better
solution. The development version (to be released after R 2.3.0)
already has a lattice-ified interface called 'hexbinplot'.


> require(gregmisc)
> require(lattice)
> #toy dataset:
> ds<-data.frame(x=rnorm(3000),y=rnorm(3000),group=rep(factor(c("A","B","C")),
> 1000))
>
> # this binscatter-function shows what I want,
> # I just would like to have it as a panel function
>
> binscatter<-function(x,y){
>  col<-rev(gray.colors(5))
>  breaks=c(1,5,10,100,500,100000)
>  h2d<-hist2d(x=x,y=y,nbins=10,same.scale=T,show=F)
>  image(h2d$x,h2d$y,h2d$counts,breaks=breaks,col=col,axes=T)
> }
>
>
> # for one group, this works fine
> A<-subset(ds,group=="A")
> binscatter(A$x,A$y)
>
> # simple xyplot does too (of course)
> xyplot(y~x|group,data=ds)
>
> # but my lattice-ified version of binscatter does not:
> # 1st attempt
> panel.binscatter<-function(x,y,subscripts,...){
>  col<-gray.colors(5)
>  breaks=c(1,5,10,100,500,100000)
>  h2d<-hist2d(x=x,y=y,nbins=10,same.scale=T,show=F)
>
> panel.levelplot(h2d$x,h2d$y,h2d$counts,subscripts=1:length(h2d$x),at=breaks,
> col.regions=col,region=T)
> }

'image' requires the z-values as a matrix and x,y values as the
margins; whereas 'panel.levelplot' needs them as vectors of the same
length (so row and column positions are repeated). To call
'panel.levelplot', you need to construct the suitable x and y values.
If I were you, I would forget about 'panel.levelplot' and construct a
call to 'grid.rect' (in the grid package) which 'panel.levelplot' ends
up doing after jumping through a lot of hoops that are irrelevant
here.

Deepayan

>
> xyplot(y~x|group,data=ds,panel=panel.binscatter)
>
> # but, this doesnt work either for one group using levelplot() :
> Ah2d<-hist2d(A$x,A$y,nbins=10,same.scale=T,show=F)
> levelplot(Ah2d$counts~Ah2d$x*Ah2d$y)
>
> # but this DOES:
> grid<-expand.grid(x=Ah2d$x,y=Ah2d$y)
> levelplot(Ah2d$counts~grid$x*grid$y)
>
> #2nd attempt doesn't work, I give up..
> panel.binscatter<-function(x,y,subscripts,...){
> col<-gray.colors(5)
> breaks=c(1,5,10,100,500,100000)
> h2d<-hist2d(x=x,y=y,nbins=10,same.scale=T,show=F)
> grid<-expand.grid(x=h2d$x,y=h2d$y)
> panel.levelplot(grid$x,grid$y,h2d$counts,subscripts=1:length(h2d$x),at=break
> s,col.regions=col)
> }
>
> xyplot(y~x|group,data=ds,panel=panel.binscatter)
>
> all suggestions welcome, thanks a lot
>
> Hans