[R] Reading and writing to S-like databases

Prof Brian Ripley ripley at stats.ox.ac.uk
Fri Sep 28 16:11:31 CEST 2001

On Fri, 28 Sep 2001, Liaw, Andy wrote:

> [snipped...]
> > 3. As I point in the document "Getting your styff organized in R",
> > I've not found any way to list the objects within a binary R file,
> > nor to select particular objects from the binary file and attach
> > only the selected ones (which would be the best solution
> > in so many cases). I wonder if future R versions could consider
> > this feature.
> I'd like to express my strong second for similar feature.  I think it would
> be very helpful for project management.  Also would be nice is something
> similar to the Unix "ls -l": giving modes, length (or dim), etc. of the
> objects in some file or the workspace.

It's not as simple as that in R.  Objects are not self-contained: they
have an environment.  And objects can share parts.  The model you both
seem to have in mind isn't appropriate for R workspaces.

It's very easy to write a function giving modes, length (or dim), etc for
a workspace, which I'll leave as an exercise for the reader.  But it will
not be like ls -l: the size of an R object is not well-defined (see
?object.size) and neither is the data (because of sharing).

Take a look at the saveload.c source code, and when you follow what it
does you will be able to work out what is feasible.

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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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