R help - Mar 2005 - Note: "The default device has been opened to honour attempt to modify trellis settings"

R-help,

I'm using a function whose end result is a trellis plot.
When I call the function I get sometimes the following message:

"Note: The default device has been opened to honour attempt to modify
trellis settings "

leading up to any plot whatsoever.

I call the package 'lattice' within the function and 'detach'
after
plotting.

I have to close the graphics device to get the desired result (and it
works only after a few more function calls)

Here is the function code

"function"<-function(somedata)
{
 ..........

library(lattice)
trellis.par.set(theme = col.whitebg())

xyplot(log.catch ~ age | yrclass , data = tmp2)

detach(package:lattice)

savePlot(file="catch curve",type="jpeg")

}

function(somedata)


Thanks in advance.

I'm running on Windows XP
> version
         _              
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    2              
minor    0.1            
year     2004           
month    11             
day      15             
language R

Luis Ridao Cruz wrote on 3/16/2005 5:16 AM:
> R-help,
> 
> I'm using a function whose end result is a trellis plot.
> When I call the function I get sometimes the following message:
> 
> "Note: The default device has been opened to honour attempt to modify
> trellis settings "
> 
> leading up to any plot whatsoever.
> 
> I call the package 'lattice' within the function and
'detach' after
> plotting.
> 
> I have to close the graphics device to get the desired result (and it
> works only after a few more function calls)
> 
> Here is the function code
> 
> "function"<-function(somedata)
> {
>  ..........
> 
> library(lattice)
> trellis.par.set(theme = col.whitebg())
> 
> xyplot(log.catch ~ age | yrclass , data = tmp2)
> 
> detach(package:lattice)
> 
> savePlot(file="catch curve",type="jpeg")
> 
> }
> 
> function(somedata)
> 
> 
> Thanks in advance.
> 
> I'm running on Windows XP
> 
> 
>>version
> 
>          _              
> platform i386-pc-mingw32
> arch     i386           
> os       mingw32        
> system   i386, mingw32  
> status                  
> major    2              
> minor    0.1            
> year     2004           
> month    11             
> day      15             
> language R
> 

Luis,

If you are trying to save a plot within a function, you are going about 
it the wrong way.

# don't call your function "function"
# "function"<-function(somedata)
my.function <- function(somedata) {
   require(lattice) # minor change here
   # next line is what's causing the message
   # trellis.par.set(theme = col.whitebg())
   trellis.device(jpeg, file = "catch_curve.jpg", theme =
col.whitebg())
   # need to explicitly print the plot to the current device
   # see FAQ 7.22
   print(xyplot(log.catch ~ age | yrclass , data = tmp2))
   # turn device off after printing
   dev.off()
   # not sure why you need to detach every time ...
   detach(package:lattice)
   #savePlot(file="catch curve",type="jpeg")
}

my.function(somedata)

--sundar