New package: g.data

David Brahm
Mon, 03 Dec 2001 16:25:02 -0000

A new package "g.data" is available on CRAN, to create and maintain
databases
that work more like the S-Plus model.

Here's the official Description for g.data (v1.2):
  Create and maintain delayed-data packages (DDP's).  Data stored in
  a DDP are available on demand, but do not take up memory until requested.
  You attach a DDP with g.data.attach(), then read from it and assign to it in
  a manner similar to S-Plus, except that you must run g.data.save() to
  actually commit to disk.

Here's a very abbreviated (Unix) example:
  g.data.attach("/tmp/mydir")             # Open package:mydir in
pos=2
  assign("x1", matrix(1, 1000, 1000), 2)  # Put data there
  g.data.save()                           # Commit to disk
  detach(2)                               # Detach package:mydir
  g.data.attach("/tmp/mydir")             # Re-attach it, no resources
used
  dim(x1)                                 # x1 is loaded only when needed!
  find("x1")                              # It still lives in
package:mydir

g.data is the end result of my post "Reading and writing to S-like
databases",
sent to R-help on Sep 28, 2001.  Thanks to all who responded, especially
Dr. Agustin Lobo <alobo at ija.csic.es> and (by reference) Ray Brownrigg
<Ray.Brownrigg at mcs.vuw.ac.nz>, who suggested using delay(); Martin
Maechler
<maechler at stat.math.ethz.ch>, Thomas Lumley <tlumley at
u.washington.edu>, Brian
D. Ripley <ripley at stats.ox.ac.uk>, and Peter Dalgaard
<p.dalgaard at biostat.ku.dk>, who helped me with platform independence
issues;
and Kurt Hornik <Kurt.Hornik at ci.tuwien.ac.at>, who cleaned it up for
CRAN.

I have one concern: g.data relies heavily on delay(), whose documentation says:
  This is an experimental feature and its addition is purely for
  evaluation purposes.
Is there any plan to deprecate delay()?

Feedback is welcome!
--
                              -- David Brahm (brahm at alum.mit.edu)

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