Re: Is it possible to call an NCL script and pass data to it from a C script?

Cathryn,

If you have downloaded NCL source code,
you may go to, say, for contour plot:
ni/src/examples/contourplot

to see examples which use NCL HLU library directly.

There are examples using Fortran or C.

Which certainly allows you to pass data (in memory)
directly to call NCL (functions).

Hope this help,

Wei

huangwei@ucar.edu
VETS/CISL
National Center for Atmospheric Research
P.O. Box 3000 (1850 Table Mesa Dr.)
Boulder, CO 80307-3000 USA
(303) 497-8924

On Nov 11, 2013, at 3:40 AM, Cathryn Meyer <cmeyer@wsi.com> wrote:

> Thank you all for all of the suggestions but I am trying to get around writing to a file at all and to be able to pass just the data array straight from the C script to the NCL script via a function call or something similar. So, it seems like I won't be able to use NCL to do that. I was just wondering if it was possible as I hadn't found anything about it in the NCL documentation or other internet sources yet.
>
>
> On Thu, Nov 7, 2013 at 6:22 PM, Dennis Shea <shea@ucar.edu> wrote:
> Interlanguage communication is either non-trivial or cumbersome.
>
> My cumbersome suggestion is to
> (1) Write a file from the C code (ascii, binary or netCDF)
> cfile = "foo.{txt/bin/nc}"
>
> (2) Use the C 'system' procedure to pass the file name to
> the NCL script. See NCL's description of Command Line Arguments
>
> http://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclCLO.shtml
>
> Not sure how to create the proper string in C but generically
> system("ncl fname="'+cfile+"' myNCLscript.ncl")
>
> (3) the nclscript would have
>
> f = adddfile(fname,"r")
> data = f->...
> or
> data = asciiread(fname ,...)
> or
> data = fbindirread(fname,...)
>
>
>
> On 11/7/13 9:54 AM, Rick Brownrigg wrote:
> Hi Cathy,
>
> There is an API to NCL functionality that allows one to *read* NCL variables/filevariables and execute scripts. Unfortunately there's no way to programmatically create and write to NCL variables and files, outside of executing lines of script. I think you're likely to have to use some sort of file to pass your 2D array. Perhaps a named pipe? In any case, you might look at the docs to see what is possible:
>
> http://www.ncl.ucar.edu/Document/Manuals/Ref_Manual/NclApi.shtml
>
> Hope that helps…
> Rick
>
> On Nov 7, 2013, at 9:39 AM, Cathryn Meyer <cmeyer@wsi.com> wrote:
>
> I have an already-existing NCL script that reads in 2D temperature data from a grib file and plots it. However I want to be able to call the NCL script from the C code that generates the temperature data and simply pass the 2D array of float values into the NCL script from within the C code instead of having to print them out to a file first that NCL reads in.
>
> Is this possible?
>
> Thanks,
> Cathy
>
> --
> Cathryn Meyer |
> w: 978 983 6598 e: cathryn.meyer@weather.com
>
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> Cathryn Meyer |
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>
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Received on Mon Nov 11 07:55:28 2013