R help - Dec 2003 - Plot grouped data: How to change x-axis? (nlme)

Hallo!

GENERAL QUESTION:
I'm trying to change the tick marks of the x-axis in a
grouped data plot (nlme). 

CONCRETE EXAMPLE:
In the example (see below) I want the x-axis to have
tick marks at 0, 6, 12, 18, 24. How can I do this? 

WHAT I TRIED
I tried "normal" methods like axis(...) but this does
not work with this plot. And I also tried xlim=c(0,24)
but the ticks are unchanged and the plot looks worse
(because of no distances to the border of the Panels).


EXAMPLE:
--
# begin example
library(lattice)
library(nlme)

# create sample data
set.seed(123)
ID<-rep(1:6, each=4)
Time<-rep(c(0,6,12,24), 6)
Y<-runif(24)
DF<-data.frame(ID, Time, Y)

GDF<-groupedData(Y ~ Time | ID, data=DF)

plot(GDF,layout=c(3,2), aspect=0.6, xlab="Months")

# end example

QUESTION: How can I get tick marks at 0, 6, 12, 18, 24
on the x-axis?

Any help will be appreciate.

Karl.

PS: Have a happy new year and keep R running!!

>>>>> "Karl" == Karl Knoblick <karlknoblich at
yahoo.de> writes:
    > QUESTION: How can I get tick marks at 0, 6, 12, 18, 24 on
    > the x-axis?

You can pass lattice arguments to plot.  (See the section under
scales in help('xyplot') for lots of details).  For your
purposes, try this:

  plot(GDF, layout=c(3,2), aspect=0.6, xlab="Months",
       scales=list(x=list(at=seq(0,24,6)))
       )

Happy New Year, Mike

-- 
Michael A. Miller                               mmiller3 at iupui.edu
  Imaging Sciences, Department of Radiology, IU School of Medicine

Karl Knoblick <karlknoblich at yahoo.de> writes:
> Hallo!
> 
> GENERAL QUESTION:
> I'm trying to change the tick marks of the x-axis in a
> grouped data plot (nlme). 
> 
> CONCRETE EXAMPLE:
> In the example (see below) I want the x-axis to have
> tick marks at 0, 6, 12, 18, 24. How can I do this? 
> 
> WHAT I TRIED
> I tried "normal" methods like axis(...) but this does
> not work with this plot. And I also tried xlim=c(0,24)
> but the ticks are unchanged and the plot looks worse
> (because of no distances to the border of the Panels).
The grouped data plots use the lattice package.  To specify an axis in
lattice calls you must use the scales argument.  Details are given in
the documentation for xyplot.