[R] Changing workspace from within an R session

[Prof Brian Ripley]

Attaching at position 1 does not work in R, as you have found.  That is in 
?attach, and in the FAQ.

As the FAQ says, using save()d objects (read-only) can do quite a lot of 
this.  You could also save the workspace, clear it, and load another saved 
image ... but it is probably easier to restart R.

On Tue, 20 Jan 2004 gerald.jean at dgag.ca wrote:

> Hello R-users,
> 
> is it possible to navigate from one workspace to the other from within an R
> session or does one has to close R and restart it from the directory where
> resides the desired workspace?
> 
> For example from Splus I have this little function, see at the end, which I
> used all the time to navigate between valid Splus directories.  I find this
> particularly usefull when I develop new functions.  Most projects I work on
> are large to extremely large, developing a function that takes a data.frame
> as input and manipulates it is very time consuming if the input data.frame
> is huge hence I have a valid Splus directory holding a few small
> data.frames, I move to it while developing the function and when I am happy
> with the function I move this function to my personnal library, always
> attached at position 2, then move back to the the current project's valid
> Splus directory.
> 
> I tried a similar approach in R, from the command line --not using a
> function yet, and I was a bit surprised by the result.  The objects already
> in the workspace, as called in R, stayed there and the objects from the
> workspace I wanted to attach were added to the current workspace and the
> workspace I was hoping to attach at pos 1 was attach at pos 2 with
> seemingly nothing in it?
> 
> > attach("/home/jeg002/splus/GlmExamples/.RData", pos = 1)
> > search()
>  [1] ".GlobalEnv"
>  [2] "file:/home/jeg002/splus/GlmExamples/.RData"
>  [3] "package:methods"
>       ...
> 
> > objects(pos = 2)
> character(0)
> 
> The little function, mentioned above, and used in Splus.
> 
> "chdir" <-
> function(datadir,  default.path = '/actuaria/jeg002/')
> {
> # Author  : Gerald Jean
> # Date    : May 1999
> # Purpose : "newdir" will be attached at position 1, and the S directory,
> #           currently at position 1 will be detached.
> # Arguments:
> #  datadir      : the directory to attach.
> #  default.path : the drive on which resides the directory to attach.
> #------------------------------------------------------------------------
> data.dir.to.detach <- search()[1]
> to.attach <- paste(default.path, datadir, "/.Data", sep = "")
> attach(to.attach, pos = 1)
> detach(what = data.dir.to.detach)
> search()
> }
> 
> Thanks for your insights,
> 
> Gérald Jean
> Analyste-conseil (statistiques), Actuariat
> télephone            : (418) 835-4900 poste (7639)
> télecopieur          : (418) 835-6657
> courrier électronique: gerald.jean at spgdag.ca
> 
> "In God we trust all others must bring data"  W. Edwards Deming
> 
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> 

-- 
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