[R] lattice log scale labels.

[Gerrit Draisma]

Dear R-helpers,

In the plot below I would like to have labels at positions 2^(3*(0:10)),
and keep the labels in the exponential format.
I tried using yscale.components.default.

*This* gives the right format of the labels:
--------
 > yscale.components.default(lim= c(0,30),log=2)
....
$num.limit
[1]  0 30
...
[1]  0  5 10 15 20 25 30
...
$left$labels$labels
[1] "2^0"  "2^5"  "2^10" "2^15" "2^20" "2^25" "2^30"
--------

and *this* gives the right locations
--------
 > yscale.components.default(lim= c(0,30),log=2,at=2^(3*(0:10)))
$num.limit
[1]  0 30
...
  [1]  0  3  6  9 12 15 18 21 24 27 30
...
$left$labels$labels
  [1] "1"          "8"          "64"         "512"        "4096"
  [6] "32768"      "262144"     "2097152"    "16777216"   "134217728"
[11] "1073741824"
--------

How can I get the format in the first example at the locations of the 
second?

Thanks,
Gerrit

-------------
x <- read.csv(text="
n,c,t,u
4,1,2,1
8,28,8,1
12,495,42,3
16,8008,256,7
20,125970,1680,31
24,1961256,11640,138
28,30421755,83776,808
32,471435600,620576,4956
36,7307872110,4700880,33719")
library(lattice)
yscale.components.log2 <- function(...){
     ans <- yscale.components.default(...)
     ans$left$labels$labels <-
         parse(text = ans$left$labels$labels)
     ans
}


# pdf("tangle_mathFig06.pdf")
xyplot(c+t+u~n,data=x,type="b", xlab="Size", ylab="Number of tangles",
    scales=list(x=list(at=4*(1:9)),y=list(log=2)),
    yscale.components=yscale.components.log2,
    auto.key=list(columns=3,text=c("(choose m n)","tangles","unique 
tangles"),
    points=FALSE,lines=TRUE))
# dev.off()