R export graphics

[Riccardo Romoli <ric.romoli@gmail.com>]

Hi, I have some trouble exporting figures from an R-org-babel session.

The code I use to generate the figure is:

#+name: my figure
#+headers: :results graphics :file /Users/riccardoromoli/Documents/ 
Dropbox/PhD/myFigure.pdf
#+begin_src R :session *R* :exports results
...
#+end_src

So, if I use : file /User/riccardoromoli/Documents/...., all works  
right, but, if I use ~/Documents/..... the R console says:
  Error in pdf(file = "~/Dropbox/PhD/myFigure.pdf") : cannot open file  
'~/Dropbox/PhD/myFigure.pdf'

I usually work in the DropBox folder because at work I have a linux  
machine instead at my home I have an OsX machine, so if I could use  
"~", I should not change the code every time I switch between the two  
different computer.

Best
Riccardo