[R] segments within a lattice graph

[John.Gavin@ubsw.com]

Hi,

I would like to use the segments command 
within a lattice graph. 
Is this allowed in R in the same way as in SPlus?
If not, what is the alternative?

For example, the following produces vertical
line segments between points in SPlus
but in R the line segments are not shown.
(I want to replicate in R what I see in SPlus.)
What is my mistake?

library(lattice)
set.seed(123)
dat <- data.frame(
aa = runif(10),
bb = runif(10),
cc = runif(10)
)
dat <- dat[order(dat$aa),]
dat
xyplot(cc ~ aa, data = dat,
 panel = function(x, y, ...)
 { # no line segements and no error is printed.
   segments(dat$aa, dat$bb, dat$aa, dat$cc)
   panel.xyplot(dat$aa, dat$cc, col = 1, pch = 1, type = "b")
   panel.xyplot(dat$aa, dat$bb, col = 2, pch = 2, type = "b")
   # no arrows but errors are printed.
   # arrows(dat$aa, dat$bb, dat$aa, dat$cc)
 }, ylim = range(dat$bb, dat$cc)
)

SPlus 6.0.5 R4 for MS Windows NT4 SP5
R 
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    1              
minor    6.1            
year     2002           
month    11             
day      01             
language R        

Regards,

John.

John Gavin <john.gavin at ubsw.com>,
Quantitative Risk Models and Statistics,
UBS Warburg, 6th floor, 100 Liverpool St.,
London EC2M 2RH, UK.
Phone +44 (0) 207 567 4289
Fax   +44 (0) 207 568 5352

Visit our website at http://www.ubswarburg.com

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