Well, time to bring out my favorite dead horse to beat:

   - http://stackoverflow.com/questions/1815606/rscript-determine-path-of-the-executing-script
   - http://stackoverflow.com/questions/3452086/getting-path-of-an-r-script

(where you already commented, so it's not like this is something new...)

I would say that any language that does not have a facility to get the path of the current file, is not 'excellent' under the criteria an experienced programmer would use for assessing it.

Now, I very well know that those criteria are different from what scientists use, but still...