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rplotlattice

xyplot bottom axis when last row has fewer panels than columns

Consider a lattice xyplot that has relation='fixed', alternating=FALSE, and as.table=TRUE.

If the last row of panels is incomplete (i.e. there are fewer panels than columns of the layout), the x-axis is not plotted. For example, panel 4 in the plot below does not have x-axis ticks/labels.

library(lattice)
d <- data.frame(x=runif(100), y=runif(100), grp=gl(5, 20))
xyplot(y~x|grp, d, as.table=TRUE, scales=list(alternating=FALSE, tck=c(1, 0)))

enter image description here

How can I add that axis?

Ideally I want axes only at bottom and left sides, and the incomplete row of panels at bottom (unlike when using as.table=FALSE, which plots the incomplete row at the top). For the example above, I'd like the axis plotted on the bottom border of panel 4, rather than in line with the x-axis of panel 5.

I know that this is easily solved with, e.g., a base graphics approach. I'm specifically interested in a lattice solution.

Solution

  • I am not a lattice expert, but I believe this might work. The idea was originally posted here. First I will regenerate the example:

    library(lattice)
set.seed(1)
d <- data.frame(x=runif(100), y=runif(100), grp=gl(5, 20))

    Next, lets define a function that will control the panel settings:

    trellis.par.set(clip = list(panel = "off"))
myPan <- function(...){
    panel.xyplot(...)
    if(panel.number() == 4) {
        at = seq(0,1,by = 0.2)
        panel.axis("bottom", at = at, outside = T,
                    labels = T, half = F)
    }
    if(panel.number() == 5) {
        at = seq(0,1,by = 0.2)
        panel.axis("bottom",at = at, outside = T,
                   labels = T, half = F)
    }
}

    Now to the plot:

    xyplot(y~x|grp, d, as.table=TRUE, 
       scales = list(
           x = list(draw = F, relation="same"),
           y = list(tck=c(1,0), alternating=F)),
       layout = c(2,3),
       panel = myPan)

    As can be seen, in the xyplot command we asked not to draw the x axis (draw = F) but later panel calls myPan function. There we specifically demand to draw x-axis for panels 4 and 5.

    output

    enter image description here

    Hope it can give you some direction for improvements.