[R] Problem with data frame when using xYplot?

[Deepayan Sarkar]

On Friday 13 May 2005 08:07 am, Sander Oom wrote:
> An off list response from Mat Soukop (thanks Mat!!) provides an even
> more elegant solution (see code below)! I have included the original
> code, so people can decide whether to plot in a single panel or in
> multiple panels. Now we have a fully functional workaround to get
> plotmeans{gplots} for multiple factors using lattice! Great!
>
> ********************
>
>
> library(Hmisc)
> library(lattice)
> tmp <-
> structure(list(Position = structure(as.integer(c(1, 2, 1, 2,
> 1, 2, 1, 2)), .Label = c("Inside", "Outside"), class = "factor"),
>      AltGeo = structure(as.integer(c(1, 1, 2, 2, 3, 3, 4, 4)), .Label =
> c("Basalt-High",
>      "Basalt-Low", "Quartz-High", "Quartz-Low"), class = "factor"),
>      Sodium = c(27.3333333333333, 26.8888888888889, 25, 18.1111111111111,
>      4.66666666666667, 5.55555555555556, 10.6666666666667, 5.66666666666667
>      ), SD = c(5.3851648071345, 2.42097317438899, 20.1618451536560,
>      15.2679766541317, 5.45435605731786, 8.09492296305393,
> 10.6183802907976, 8.06225774829855), Nobs = c(9, 9, 9, 9, 9, 9, 9, 9),
> Lower =
> c(25.5382783976218,
>      26.0818978307592, 18.2793849487813, 13.0217855597339,
> 2.84854798089405, 2.85724790120425, 7.12720656973412, 2.97924741723382),
> Upper = c(29.1283882690448,
>      27.6958799470186, 31.7206150512187, 23.2004366624884,
> 6.48478535243929, 8.25386320990686, 14.2061267635992, 8.35408591609952)),
> .Names = c("Position",
> "AltGeo", "Sodium", "SD", "Nobs", "Lower", "Upper"), row.names = c("1",
> "2", "3", "4", "5", "6", "7", "8"), class = "data.frame")
> tmp$PosNum <- unclass(tmp$Position)
> tmp
> (labs <- unique(tmp$Position))
> # plot factor levels in seperate panels
> xYplot(Cbind(Sodium,Lower,Upper) ~ PosNum|AltGeo, data=tmp, nx=FALSE,
>    xlim=c(0.5,2.5),
>    ylim=c(min(tmp$Lower)-1,max(tmp$Upper)+1),
>    scales = list(x = list(at=seq(1, 2, by=1), labels = labs)),
>    xlab="Position", ylab="Sodium"
>    )

Just out of curiousity, does replacing the 'xlim' and 'scales' arguments above 
by 

xlim = levels(tmp$Position)

do the same thing? It should with xyplot (which also allows the x variable to 
be a factor), but xYplot may be bypassing that.

Deepayan