From ripley@stats.ox.ac.uk  Sat Jan  2 07:47:53 1999
From: ripley@stats.ox.ac.uk (Prof Brian D Ripley)
Date: Sat, 2 Jan 1999 07:47:53 +0000 (GMT)
Subject: .C
In-Reply-To: <199901020546.WAA09870@ale.atd.ucar.edu>
Message-ID: <Pine.GSO.4.05.9901020733370.1627-100000@auk.stats>

On Fri, 1 Jan 1999, Steve Oncley wrote:

> Happy 1999!
> 
> I've been celebrating the holidays by (finally) getting to the port of our 
> S+ NetCDF routines to R, which I'm trying to make into a library.  At the 
> moment, there are two issues I'd appreciate advice on:

As people kept telling me, a `package' in R.

> 1. Is support for mode "single" data planned anytime soon in R?  A lot of
> our NetCDF files contain "single" data and having to coerce into "double"
> will increase the use of R memory drastically (and slow things down).

Not `soon' from the responses to my requests.  I think you exaggerate
though: this can at most double the memory usage, and depending on the
machine and if you actually compute with the data (rather than move it
around) may have negliglible speed penalty. Remember too that anything done
with the data inside S-PLUS 3.x (and R, AFAIK) will make several
double-precision copies.

> 2. Is there support for "pointer to pointer" arguments to .C?  NetCDF files
> contain the data attributes, which aren't known until the files are read.
> Our S+ code defines a dummy variable for the data dimensions, which are 
> redefined (calling "S_alloc") and set within the C code once they are known.
> The appended example works in S+ using the pointers= argument in .C.  
> Is there a way to do this in R?

Actually, there is no longer a way to do this in S-PLUS: the pointers=
argument is not available in S-PLUS 5.x.  I think you need to re-think your
strategy: an alternative can be seen in the rpart code.


-- 
Brian D. Ripley,                  ripley@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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.C
Prof Brian D Ripley