[R] compress data on read, decompress on write
Ramon Diaz-Uriarte
rdiaz02 at gmail.com
Thu Feb 28 23:47:00 CET 2008
Dear Prof. Ripley,
Thanks a lot. I've just looked at Rcompression and it seems to do
exactly what I need, though it requires having zlib and bzip2
installed (and I am not sure if this will deter some windows users).
I'll also check connections.c, which might be a way to go, or else
wait for the release of that version of our package until R 2.7.0 is
out.
Best,
R.
On Thu, Feb 28, 2008 at 8:53 PM, Prof Brian Ripley
<ripley at stats.ox.ac.uk> wrote:
> One solution is likely to be the Omegahat package Rcompression.
>
> Otherwise, R does have internal facilities to do internal (gzip)
> compression and decompression (e.g. see the end of
> src/main/connections.c), and you could make creative use of serialization
> to do the compression.
>
>
> On Thu, 28 Feb 2008, Ramon Diaz-Uriarte wrote:
>
> > Dear All,
> >
> > I'd like to be able to have R store (in a list component) a compressed
> > data set, and then write it out uncompressed. gzcon and gzfile work in
> > exactly the opposite direction. What would be a good way to handle
> > this?
> >
> > Details:
> > ----------
> >
> > We have a package that uses C; part of the C output is a large sparse
> > matrix. This is never manipulated directly by R, but always by the C
> > code. However, we need to store that data somewhere (inside an R
> > object) for further calls to the functions in our package. We'd like
> > to store that matrix as part of the R object (say, as an element of a
> > list). Ideally, it would be stored in as compressed a way as possible.
> > Then, when we need to use that information, it would be decompressed
> > and passed to the C function.
> >
> > I guess one way to do it is to have C deal with the compression and
> > uncompression (e.g., using zlib or the bzip2 libraries) and then use
> > readBin, etc, from R. But, if I can, I'd like to avoid our C code
> > having to call zlib, etc, so as to make our package easily portable.
>
> As from R 2.7.0 you will be able to make use of zlib on effectively all
> platforms, since it has a public interface on Windows.
>
>
>
> >
> > Thanks,
> >
> > R.
> >
> > --
> > Ramon Diaz-Uriarte
> > Statistical Computing Team
> > Structural Biology and Biocomputing Programme
> > Spanish National Cancer Centre (CNIO)
> > http://ligarto.org/rdiaz
>
> --
> 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
>
--
Ramon Diaz-Uriarte
Statistical Computing Team
Structural Biology and Biocomputing Programme
Spanish National Cancer Centre (CNIO)
http://ligarto.org/rdiaz
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