[R] R graph strip in Greek Letters

[Sundar Dorai-Raj]

zj yang wrote:
> Hi all,
> 
> I have one question on xyplot() function.
> 
> I am trying to produce a graph by this code.
> 
> tmp <- data.frame(a=rnorm(20),
>                  b=rnorm(20),
>                  rho=factor(rep(1:2, c(10,10))),
>                  k=factor(rep(1:5,4)))
> 
> tmp.lattice <-
> xyplot(a ~ b | rho*k, data=tmp,
>       par.strip.text=list(font=5),
>       strip=function(...) strip.default(..., strip.names=c(TRUE,TRUE)))
> 
> names(tmp.lattice$condlevels) <- c("k","r")
> tmp.lattice
> 
> You can see that on the strip, I have both k and rho in greek letters. I
> ONLY want rho to be greek letter and remain k as an ordinary lower case 'k'.
> The other question is, can I change the ":" into "=" in the strip? Thanks a
> lot.
> 
> Zijiang
> 
> 	[[alternative HTML version deleted]]
> 
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Does this help?

library(lattice)
trellis.par.set(theme = col.whitebg())

tmp <- data.frame(a = rnorm(20),
                   b = rnorm(20),
                   rho = factor(rep(1:2, c(10,10))),
                   k = factor(rep(1:5,4)))

strip.math <- function(which.given, which.panel, var.name, 
factor.levels, ...) {
   vn <- var.name[which.given]
   fl <- factor.levels
   expr <- paste(vn, "==", fl, collapse = ",")
   expr <- paste("expression(", expr, ")", sep = "")
   fl <- eval(parse(text = expr))
   strip.default(which.given, which.panel, vn, fl, ...)
}

xyplot(a ~ b | rho*k, data=tmp, strip = strip.math)

The "eval(parse(text = ...)))" is the only way I know how to build a 
valid expression for the plotmath functions. See ?plotmath for more 
information.

HTH,

--sundar