Index.cond does not rearrange the panels in lattice

Question

I am following the book "R in action" P389 example to arrange hist panels in the following lattice graph:

library(lattice)
graph1 <- histogram(~ height | voice.part, data = singer,
                    main = "Heights of Choral Singers by Voice Part")
graph2 <- densityplot(~ height, data = singer, group = voice.part,
                      plot.points = FALSE, auto.key = list(columns = 4))
plot(graph1, position=c(0, .3, 1, 1))
plot(graph2, position=c(0, 0, 1, .3), newpage = FALSE)

As instruction from the book, I use index.cond to change the order of the graph, like

plot(graph1, position = c(0, .3, 1, 1),
     index.cond = list(c(2, 4, 6, 8, 1, 3, 5, 7)))

But the order in the graph does not change. Can anyone help me of this? I also notice index.cond is not in the help of ?plot

Answer 1

"index.cond", as other arguments described in ?xyplot are either passed to the functions that create "trellis" objects or to the update methods. So, in this case, you can

create "graph1" by passing "index.cond" to histogram:

histogram(~ height | voice.part, data = singer, 
          main = "Heights of Choral Singers by Voice Part", 
          index.cond = list(c(2, 4, 6, 8, 1, 3, 5, 7)))

, use update:

update(graph1, index.cond = list(c(2, 4, 6, 8, 1, 3, 5, 7)))

or use "[":

graph1[c(2, 4, 6, 8, 1, 3, 5, 7)]