[R] opendap accessibility on Windows

[Michael Sumner]

On Tue, 7 Jul 2015 at 01:38 Christina Hernandez <chernandez at gmri.org> wrote:

> Hello,
>
> I am working on a project where we are accessing large data files via
> opendap. Myself and two of the higher-ups on the project are working on
> Windows machines, and we have been unable to access remote files using the
> ncdf4 package. We have followed the package author's notes for installation
> on a Windows machine, and we have successfully installed the netcdf-4
> libraries and the ncdf4 R package.


I've done this on Windows by using Unidata's DLLs that they provide for
download and including them in the build process for ncdf4:

http://www.unidata.ucar.edu/software/netcdf/docs/winbin.html

But this leaves you several branches out with an unsupported package build
(by CRAN) and with Microsoft compiled opendap files.

Please note that you don't need ncdf4 for NetCDF4 faciilties, RNetCDF (and
ncdf) can be built with that version and many features (including remote
file access) work fine.

I would aim for working on Linux, it's much more straightforward to
build/get these tools there. It would be excellent if CRAN's win builder
had these standard libraries, and others like HDF4/5,  but I don't know if
that is possible.

cheers, Mike.

However, the program still works only on local files. It is not an issue
> with connectivity of my machine since I am able to remotely access these
> same data files using Matlab.
> I then attempted to follow the package author's notes on cross-compiling
> in a Linux environment, I was using a Ubuntu Virtual Box. These notes are
> available here:
> http://cirrus.ucsd.edu/~pierce/ncdf/how_to_build_on_windows.html
> However, I do not really know what I'm doing and I was unable to
> successfully cross-compile the dependencies. Has anyone dealt with this on
> a Windows machine? Is there a different way to access remote files through
> R? \We have considered writing a Python script that can be run from within
> an R program, so that users that are only familiar with R can still access
> remote files without downloading a lot of large files.
> Any advice is appreciated.
>
>
> Christina Hernandez
> Research Assistant
> Ecosystem Modeling Lab
> Gulf of Maine Research Institute
> chernandez at gmri.org
>
>
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>
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