[R] relative referencing for filenames &etc

[Prof Brian Ripley]

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