[R] R doesn't recognize R_HOME value

[Prof Brian Ripley]

On 25/07/2012 09:14, peter dalgaard wrote:
>
> On Jul 25, 2012, at 07:58 , Prof Brian Ripley wrote:
>
>> On 24/07/2012 21:57, Kirk Fleming wrote:
>>> ???
>>>
>>> Windows 7 is where I'm seeing the problem.
>>>
>>> The root problem: while I have R_HOME legitimately specified within Windows
>>> 7, and issuing 'set R_HOME' from the command line returns exactly the path
>>> I've specified, doing a Sys.getenv('R_HOME') from R returns a completely
>>> different path.
>>>
>>> I ask, "What would cause a Sys.getenv() call to return a different value
>>> than the OS does?"
>>
>> A different process and hence a different environment ... this is why they are called 'environment variables' and are specific to a process.
>>
>> 'The command line' is actually a shell process, not the OS itself. Setting environment variables in a shell affects only that shell and those which inherit from it.
>>
>> See ?R_HOME in R, which tells you that in the R process 'is normally set on startup'.   'Normally' because there are many ways to start R (embedded, for example: see 'Writing R Extensions'), and you have not actually told us how you started R.  But Rgui.exe and Rterm.exe do always set R_HOME.
>
>
> Notice also that R_HOME represents R's own knowledge of its installation directory, where it looks for various support files, the default package library, etc.
>
> R sets R_HOME for itself; even if you could, you really do not want
> to  override it. Try looking at ?Startup for the correct ways to specify
alternative locations of profile files, etc.

Well, I was being careful, and the following may be too technical for 
R-help.

R's own front-ends set R_HOME for themselves, but embedded versions of R 
may well get it from somewhere else and for such uses the end-user may 
need to specify it as an environment variable in the process embedding 
R.  Alternative front-ends (e.g. RStudio) are examples of embedding and 
do need a way to find R's own installation directory (which may or may 
not be recorded in the Windows Registry on Windows).  Rgui.exe uses its 
own path to find R_HOME.

-- 
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