R lattice: add text to a scatterplot on x-axis considering grouping

Question

I have a data set with values yat two dates xfor two groups gp. Additional I have for each of these values a figure n which I would like to add at the x-axis. Here is the code to produce the data and the figure:

set.seed(1234)
data0 <- expand.grid(gp = c("A","B")
                  , x = 1:2
                  )
data0$y <- round(runif(4),2)
data0$n <- round(100*runif(4),0)
data0

#   gp x    y  n
# 1  A 1 0.11 86
# 2  B 1 0.62 64
# 3  A 2 0.61  1
# 4  B 2 0.62 23

xyplot(y ~ x | gp, data=data0
       , panel = function(...) {
           panel.xyplot(...)
           panel.text(1,0.1,86)
           panel.text(2,0.1,64)           
       }
       )

And here is the the figure:

I would like that the correct n are on the x-axis that is: n should be added at the x-axis considering the grouping gp and x. Any idea how to cope with this?

Answer 1

You can use subscripts to keep track of each row in your panel functions.

xyplot(y ~ x | gp, data=data0,#subscripts=TRUE,
       panel = function(x,y,subscripts,...) {
           panel.xyplot(x,y,...)
           panel.text(data0$x[subscripts],0.1,data0$n[subscripts])
       }
)

You might want to adjust where you put the text (y=0.1) to avoid almost overplotting the data.

(EDIT: commented out subscripts=TRUE which isn't necessary here.)