[R] How to adjust y-axis when using panel.densityplot within histogram function

[David Winsemius]

On Jul 27, 2011, at 9:15 AM, Sébastien Bihorel wrote:

> Hi
>
> I would like to superimpose group-specific densityplots on top of an  
> overall
> histogram using panel.histogram and panel.densityplot. Furthermore,  
> I would
> like to automatically adjust the range of the y-axis to take into  
> account
> the ranges of both histogram and densityplot. This last part is  
> where I have
> a problem. I believe using the prepanel argument of histogram is  
> typically
> the way to go, but I did not have very much success with my  
> attempts. Is
> this the way to go, or should I calculate the range outside the  
> histogram
> call using some stat function (density?) on each group and use it as  
> a ylim
> argument?
>
> Any advise would be greatly appreciated.
>
> Thank you
>
> Sebastien
>
> require(lattice)
> set.seed(12345)
>
> foo1 <- data.frame(x=rnorm(100,0,0.1),grp=1)
> foo2 <- data.frame(x=rnorm(100,2,1),grp=2)
>
> foo <- rbind(foo1,foo2)
>
> #
> # Some code to calculate ylim...
> #
>
> histogram(~x,data=foo,groups=grp,
>  #prepanel=function(x,type,groups,...){???},
>  panel=function(x,type,groups,...){
>    panel.histogram(x,col='transparent',...)
>    panel.densityplot(x,groups=groups,...)
>  },
>  #ylim=ylim,
>  type='density')

Use densityplot instead of histogram as the wrapping function so its  
more extreme ranges are respected. You do get an error when you do  
that saying that 'breaks' is invalid, but if you read the ?histogram  
page, it suggests that setting breaks=NULL might produce acceptable  
default behavior, and that seems to be so in this case:

densityplot(~x,data=foo,groups=grp,
  #prepanel=function(x,type,groups,...){???},
  panel=function(x,type,groups,...){
          panel.densityplot(x,groups=groups,...)
          panel.histogram(x,col='transparent', breaks = NULL, ...)

  } )

>
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David Winsemius, MD
West Hartford, CT