lattice xscale.components: different ticks on top/bottom axis
On Fri, Mar 11, 2011 at 12:28 AM, <Boris.Vasiliev at forces.gc.ca> wrote:
Good afternoon,
I am trying to create a plot where the bottom and top axes have the same
scale but different tick marks. ?I tried user-defined xscale.component
function but it does not produce desired results. ?Can anybody suggest
where my use of xscale.component function is incorrect?
For example, the code below tries to create a plot where horizontal axes
limits are c(0,10), top axis has ticks at odd integers, and bottom axis
has ticks at even integers.
library(lattice)
df <- data.frame(x=1:10,y=1:10)
xscale.components.A <- function(...,user.value=NULL) {
?# get default axes definition list; print user.value
?ans <- xscale.components.default(...)
?print(user.value)
?# start with the same definition of bottom and top axes
?ans$top <- ans$bottom
?# - bottom labels
?ans$bottom$labels$at <- seq(0,10,by=2)
?ans$bottom$labels$labels <- paste("B",seq(0,10,by=2),sep="-")
?# - top labels
?ans$top$labels$at <- seq(1,9,by=2)
?ans$top$labels$labels <- paste("T",seq(1,9,by=2),sep="-")
?# return axes definition list
?return(ans)
}
oltc <- xyplot(y~x,data=df,
scales=list(x=list(limits=c(0,10),at=0:10,alternating=3)),
? ? ? ? ? ? ? xscale.components=xscale.components.A,
? ? ? ? ? ? ? user.value=1)
print(oltc)
The code generates a figure with incorrectly placed bottom and top
labels. ?Bottom labels "B-0", "B-2", ... are at 0, 1, ... and top labels
"T-1", "T-3", ... are at 0, 1, ... ?When axis-function runs out of
labels, it replaces labels with NA.
It appears that lattice uses top$ticks$at to place labels and
top$labels$labels for labels. ?Is there a way to override this behaviour
(other than to expand the "labels$labels" vector to be as long as
"ticks$at" vector and set necessary elements to "")?
Well, <top|bottom>$ticks$at is used to place the ticks, and $labels$at
is used to place the labels. They should typically be the same, but
you have changed one and not the other. Everything seems to work if
you set $ticks$at to the same values as $labels$at:
## - bottom labels
+ ans$bottom$ticks$at <- seq(0,10,by=2)
ans$bottom$labels$at <- seq(0,10,by=2)
ans$bottom$labels$labels <- paste("B",seq(0,10,by=2),sep="-")
## - top labels
+ ans$top$ticks$at <- seq(1,9,by=2)
ans$top$labels$at <- seq(1,9,by=2)
ans$top$labels$labels <- paste("T",seq(1,9,by=2),sep="-")
Also, can user-parameter be passed into xscale.components() function? (For example, locations and labels of ticks on the top axis). ?In the code above, print(user.value) returns NULL even though in the xyplot() call user.value is 1.
No. Unrecognized arguments are passed to the panel function only, not
to any other function. However, you can always define an inline
function:
oltc <- xyplot(y~x,data=df,
scales=list(x=list(limits=c(0,10), at = 0:10, alternating=3)),
xscale.components = function(...)
xscale.components.A(..., user.value=1))
Hope that helps (and sorry for the late reply).
-Deepayan