[Rd] ncdf with opendap/dods support

[Russell Moffitt]

Aloha,

I just made some quick hacks on the configure script with the 'ncdf' 
package to make it link with the opendap/dods libraries (opendap.org) 
rather than the netcdf api library.  Basically, this allows a user to 
interact in R with a remotely served dataset as if it were a netcdf file 
on the local filesystem (read-only).  Functionality with local files 
should continue to work as well.  This opendap feature should be greatly 
useful for a number of fields of scientific computing, including 
oceanography and climate modelling, where a huge number of data sets are 
already served via opendap around the world.

In order to do this, the user must install the opendap/dods netcdf 
libraries on the system and then run
R CMD INSTALL --configure-args="-with-dods=$DODS_INSTALL_DIR" 
ncdf_1.3-dods.tar.gz
where $DODS_INSTALL_DIR is wherever the opendap lib and include 
directories are found.

My modifications are small and unelegant, but it works, providing that 
the user can successfully install the opendap libraries.  I am neither a 
compile guru nor do I have very much experience using and developing for 
R.  Therefore, I would like to see if anyone would be willing to help me 
make this modification into a more official package/patch that can be 
shared with other R users.  The biggest obstacle for me is making 
binaries for Windows.  Precompiled opendap libraries are available for 
windows, so this should be possible.  B Ripley has compiled the 'ncdf' 
package for windows, and this version should be exactly the same except 
for different external libraries.

This same modification should also be possible for the RNetCDF/nvar 
packages since they use the same support libraries.  I just happened to 
try it with ncdf first.  Which package do more people tend to use/like 
for accessing netcdf files?

Please let me know if you can provide some assistance in making this 
modified package as easy to install as possible on 
unix/linux/windows/etc...  I can provide more info about the opendap 
library and what is required to link to it if you ask.

Mahalo,
Russell

P.S.  I imagine that this opendap support in R will allow us to list R 
on opendap.org's list of client applications, giving R some more exposure.