[R] Varying grid.rect in different panels of a Lattice plot

[Deepayan Sarkar]

On Wednesday 16 March 2005 18:48, Leon Barmuta wrote:
> Dear r-help,
>
> Sleep-deprivation from having 2 youngsters under 2 around the house
> is fuzzing my brain, so please be gentle if the answer to this query
> is obvious!
>
> In the example below, I'm trying to use grid.rect to add grey
> rectangles to the panels of a lattice plot to indicate which months
> spawning occurred of a (very cute) native Tasmanian fish. The fish in
> the two lakes spawned at slightly different times, so grid.rect needs
> to be conditioned on when spawning happened in each lake. However,
> the panel function I wrote first, and reproduce below, inserts grey
> rectangles for all dates that spawning occured pooled across the two
> lakes. So after dreging r-help, I've messed with subscripts and tried
> fiddling with panel.number, but can't get this to work. Any
> suggestions most welcome!

If I understand you right, you could do something like:



myPanel <- function(x, y, groups, subscripts, ...)
{
    grid.rect(x = unit(x[groups[subscripts] == "Y"], "native"),
              just="left", width=unit(31, "native"), # a bit of a fudge
              gp = gpar(col="transparent", fill="light grey"))
    panel.xyplot(x, y, ...)
}


xyplot(Catch ~ Plotdate | Lake, type="b",
       groups = Spawning,
       panel = myPanel,
       layout= c(1,2), xlab="",
       scales = list(x=list(rot = 45, at=as.numeric(Plotdate),
                     labels=format(Plotdate, "%b%Y"))))



There's nothing (much) special about 'groups', you could also do 


myPanel <- function(x, y, flag, subscripts, ...)
{
    grid.rect(x = unit(x[flag[subscripts] == "Y"], "native"),
              just="left", width=unit(31, "native"), # a bit of a fudge
              gp = gpar(col="transparent", fill="light grey"))
    panel.xyplot(x, y, ...)
}


xyplot(Catch ~ Plotdate | Lake, type="b",
       flag = Spawning,
       panel = myPanel,
       layout= c(1,2), xlab="",
       scales = list(x=list(rot = 45, at=as.numeric(Plotdate),
                     labels=format(Plotdate, "%b%Y"))))



except that if you had your variables in a data frame (supplied as the 
'data' argument) and not in your search path, anything supplied as 
'groups' would also be evaluated in the data frame.

Deepayan



> # Make up a short data set
>
> library(lattice)
> library(grid)
>
> Lake <- rep(c("Crescent","Sorell"), each=13)
> Spawning <- c("Y", rep("N",7), rep("Y",4), rep("N",8), rep("Y",5),
> "N") Catch <- rpois(26, 30) # fake data
> Plotdate <- rep(seq(as.Date("2000/10/1"), by="month", length=13),2)
>
> trellis.device(theme=col.whitebg())
>
> # panel function that doesn't quite work
>
> myPanel <- function(x, y, ...) {
>   grid.rect(x=unit(Plotdate[Spawning == "Y"], "native"),
>        just="left", width=unit(31, "native"), # a bit of a fudge
>        gp=gpar(col="transparent", fill="light grey"))
>        panel.xyplot(x, y, ...)}
>
> xyplot(Catch ~ Plotdate|Lake, type="b",
>        panel=myPanel,
>        layout=c(1,2), xlab="",
>        scales = list(x=list(rot = 45, at=as.numeric(Plotdate),
>                      labels=format(Plotdate, "%b%Y"))))
>
> Regards,
>
> Leon
>
> -------------------------
> Dr Leon A. Barmuta, Senior Lecturer in Zoology
> School of Zoology & TAFI, University of Tasmania, Private Bag 5,
> Hobart, Tasmania 7001, Australia
> Phone (03) 6226 2785;  Fax (03) 6226 2745; International callers
> replace (03) with +61 3
> School of Zoology web page: http://www.scieng.utas.edu.au/zoo/
> My web page:
> http://www.scieng.utas.edu.au/zoo/pagedetails.asp?lpersonId=222