Error in stripplot (was Re: [R] stripplot gets weird) (PR#195)

After thinking that the name difference was a problem, or that attaching
the dataframe was a problem, I think it might be something to do with
internal representation of numbers:

aitken/Exam9> R

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impurity.df<-read.table("impurities.dat",header=T)
impurity.df

   supplier1 supplier2
1        3.8       1.8
2        3.5       2.2
3        4.1       1.3
4        2.5       5.1
5        3.6       4.0
6        4.3       4.7
7        2.1       3.3
8        2.9       4.3
9        3.2       4.2
10       3.7       2.5
11       2.8       5.4
12       2.7       4.6

supp.diff<-impurity.df$supplier1-impurity.df$supplier2
stripplot(supp.diff,method="stack")

Warning in y + (unlist(xo) - 1) * offset * csize : longer object length
        is not a multiple of shorter object length
Error: x and y lengths differ

dput(supp.diff)

c(2, 1.3, 2.8, -2.6, -0.4, -0.4, -1.2, -1.4, -1, 1.2, -2.6, -1.9
)

supp.diff<-c(2, 1.3, 2.8, -2.6, -0.4, -0.4, -1.2, -1.4, -1, 1.2, -2.6,

-1.9
+ )

stripplot(supp.diff,method="stack")

Works!!!

The bit of code inside stripplot that is playing up is intended to
determine where there are repeated values, and create a sequence
numbering the values:
    f <- function(x) seq(length(x))
    for (i in 1:n) {
        x <- groups[[i]]
        y <- rep(i, length(x))
        if (method == 2) 
            y <- y + runif(length(y), -jitter, jitter)
        else if (method == 3) {
            xg <- split(x, factor(x))
            xo <- lapply(xg, f)
            x <- unlist(xg)
            y <- y + (unlist(xo) - 1) * offset * csize