R help - Oct 2009 - dev.copy(postscript,...) generates a disrupted string

Dear R-Users,

I have the following problem: I would like to create a postscript file  
containing an r-plot with the string "\\vartheta" in it (reason: this
is later converted to the TeX-string "\vartheta" and a vartheta is  
printed in the figure). In the minimal example below, the problem is  
that the created postscript file does _not_ contain the string "\\vartheta 
" as a whole, but rather the following code:
...
284.38 36.00 (\\v) 0 ta
-0.300 (ar) tb
0.480 (theta) tb gr
...
The problem is, that the program which converts the created .ps file  
to a .tex file does not understand this disrupted string. Why does the  
dev.copy(postscript,..)-command produce such an output and how can I  
prevent it from doing so? If I use a different string such as "\\v_i",
then everything works fine and "\\v_i" appears as a whole string in  
the postscript file. So why does it not work for "\\vartheta"?

Thanks in advance,

Marius

====Code=========================================================
remove(list=objects())
library(lattice)

x=c(1,2,3)
y=c(1,4,9)

xyplot(y~x,xlab=list("\\vartheta"))
dev.copy(postscript,color=F,horizontal=F,onefile=F,file="myfile.ps")
dev.off()

On Sat, Oct 24, 2009 at 9:09 PM, Marius Hofert <m_hofert at web.de>
wrote:
> Dear R-Users,
>
> I have the following problem: I would like to create a postscript file
> containing an r-plot with the string "\\vartheta" in it (reason:
this is
> later converted to the TeX-string "\vartheta" and a vartheta is
printed in
> the figure). In the minimal example below, the problem is that the created
> postscript file does _not_ contain the string "\\vartheta" as a
whole, but
> rather the following code:
> ...
> 284.38 36.00 (\\v) 0 ta
> -0.300 (ar) tb
> 0.480 (theta) tb gr
> ...
> The problem is, that the program which converts the created .ps file to a
> .tex file does not understand this disrupted string. Why does the
> dev.copy(postscript,..)-command produce such an output and how can I
prevent
> it from doing so? If I use a different string such as "\\v_i",
then
> everything works fine and "\\v_i" appears as a whole string in
the
> postscript file. So why does it not work for "\\vartheta"?
 Because postscript() doesn't know what you want to do with \vartheta,
and thinks you want to typeset the text itself. So it very cleverly
adjusts the spacing between the letters to look nice - this is called
'kerning'. This means the text has to be set by postscript in several
parts.

 You can do greek characters in plots - see help(plotmath).

Barry