On Mon, 19 Apr 2010, Frank E Harrell Jr wrote:
Barry Rowlingson wrote:
On Sun, Apr 18, 2010 at 11:30 PM, kMan <kchambe...@gmail.com> wrote:
It was my understanding that .Rdata files were not very portable, and do
not
natively handle queries. Otherwise we'd all just use .RData files instead
of
farming the work out to SQL drivers & external libraries, and colleagues
who
use, e.g. SAS or SPSS would also have no trouble with them.
The "platform" in "cross-platform" to me generally means the
operating system on which a program is running - and .Rdata files are
perfectly portable between R on Linux, MacOSX, Windows, Solaris etc
versions. You didn't mention portability to other statistical
packages. You also didn't mention needing SQL, or what you wanted to
do with your databases. I figured I'd just mention .Rdata files for
completeness!
There's also RJDBC and RODBC which can interface to anything with a
JDBC or ODBC interface on your system.
A .RData file could be considered as a serverless NoSQL database.
There's a GSOC proposal to investigate interfaces to NoSQL databases
and some info here:
http://rwiki.sciviews.org/doku.php?id=developers:projects:gsoc2010:nosql_interface
Isn't it odd that the open-source R community has developed functions
for reading in proprietary SAS and SPSS format files, but (AFAIK) the
commercial sector doesn't seem to support reading data from
open-sourced and open-specced R .Rdata files?
Barry
Hi Barry,
Stat Transfer can read and write R binary data frames (.rda files).
Yes, but that is a considerable restriction (and other programs can do
similar things). I suspect it means 'data frames with columns from a
prespecified small set of types' saved in an RDA2 gzipped binary xdr
format.
BTW, .rda and .RData are simply convenient file extensions: the first
is more convenient in the Windows world. They are from one of a
collection of many different formats, identified by the file 'magic'
headers.
I am not so sure about 'open-specced R .Rdata files'. In so far as
there is a spec, I wrote it in 'R Internals' and it is not a full
spec. Mainly because many of the details are only relevant to R
itself, such as how you read environments and some of the details of
the object headers.
Had the RDA formats been written with the intent that they would be
used other than to read all the objects they contain into R, they
would have been structured differently with a lot more metadata.
That has been noted for RDA3, but introducing such a format would be a
major step and is not imminent.
--
Brian D. Ripley, rip...@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
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