relative referencing for filenames &etc

Thank you both for your helpful suggestions.  My ignorance of R prevents me
from understanding exactly how to

  "...run from a shortcut, appending DATADIR=J:/foo/bar to the
   command line"

but I assume that Appendix C of "S Programming" will help me there -- I was
unaware of this material when I posted my question.  I was able to success-
fully use the following:

  > Sys.putenv("R_DATADIR"="Z:/.../raw")
  > Sys.getenv("R_DATADIR")

     R_DATADIR
  "Z:/.../raw"

  > file.path(Sys.getenv("R_DATADIR"), "RAWDATA.xls")

  [1] "Z:/.../raw/RAWDATA.xls"

Using this type of code, I should be able to "point" R at data and output
directories.  In my industry, programmers are required to save their SAS
log files for auditing purposes, and knowing that R has similar capabilities
is very helpful.

Again, thanks for your help.  Kind regards,


    Greg




--- Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:

On Tue, 28 Feb 2006, Uwe Ligges wrote:

On Mon, 27 Feb 2006, Greg Tarpinian wrote:

BACKGROUND:
I use SAS on a daily basis and one of its most powerful features in a
production environment is the use of LIBNAME and FILEREF statements, e.g.:


PROC PRINTTO LOG = "&LOGDIR.\data processing.log" NEW;
RUN;
PROC IMPORT
   DATAFILE= "&DATADIR.\blah.xls"
   OUT = TEMP
   DBMS = EXCEL REPLACE;
    SHEET = "Sheet1";
    GETNAMES = YES;
RUN;


Properly setting up SAS Shortcuts in the WinXP environment, or (say)
the UNIX equivalent of batch files in the UNIX environment will cause
SAS to autoexecute (say) an INIT.SAS file that automatically assigns
the LOGDIR and DATADIR macro variables used above.  This is extremely
convenient because it makes the SAS code more portable from project to
project.


MY QUESTION:
Is it possible to use this kind of relative file and directory referencing
from within R?

Perhaps you are looking for ?setwd

Another idea is to use environment variables.  So if in an R function I
have

     xls_file <- file.path(Sys.getenv("DATADIR"), "blah.xls")

I can R run from a shortcut, appending DATADIR=J:/foo/bar to the command
line.

--
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595