[R] different x-axes in Lattice

[Robert Ruser]

I use lattice package and 'barchart' to build a chart. I have a
problem with setting different x-axes. Some x categories are missing
but they are display and I don't want. I use scales = list(y =
"free",x="free") but it works only for y-axes. Simple example:

package(lattice)
barchart(yield ~ variety | site, data = barley,
        groups = year, layout = c(1,6),
        scales = list(y = "free",x="free"),
        auto.key=list(rectangles = TRUE, space = "bottom"),
        )

Let's assume that in the first panel  'Waseca'  the category 'Velvet'
are not available in data but in the chart there is a empty place. If
more categories are not available it looks bad. Simple modification to
illustrate my problem:

barley2 <- barley[barley[,2]!="Velvet" | barley[,4]!="Waseca",]
barchart(yield ~ variety | site, data = barley2,
        groups = year, layout = c(1,6),
        scales = list(y = "free",x="free"),
        auto.key=list(rectangles = TRUE, space = "bottom"),
        )


Robert