floor function for grads

[Habib Amini]

Dear
I want to overlay tow composite maps of vector wind and omega from CDC NOAA.
How can I do it in GrADS? If you do it please attach to me its script.

Best Regards


On 9/16/08, Arlindo da Silva <dasilva at alum.mit.edu> wrote:
>
>  On Mon, Sep 15, 2008 at 12:09 PM, P.Romero <romero619 at hotmail.com> wrote:
>
>>  I need to implement the FLOOR function.
>>
>> What's the best/easiest way to get this done?
>>
>> I'm guessing as a UDF, but I need some help on setting up the C code…
>>
>
>
> It should be relatively simple to do it as a dynamic UDF for v1.9.0-rc1.
> Here is the example of the sqrt function implemented as such:
>
>
>
> http://opengrads.cvs.sourceforge.net/*checkout*/opengrads/grads/udf/dll/my_sqrt.c?revision=1.2
>
>
>
> Basically, you just need to replace the sqrt() call with floor() and
> removed the test for positive values. Everything else should stay the same.
> (You could start with a global search+replace "sqrt" -> "floor").
>
>
> Here are some quick instructions to have your function built. Start with
> the  sources from
>
>
>  grads-1.9.0-rc1-gex-r2.tar.gz<http://downloads.sourceforge.net/opengrads/grads-1.9.0-rc1-gex-r2.tar.gz?modtime=1207263579&big_mirror=0>
>
>
>
> Then
>
>
> % tar xvfz grads-1.9.0-rc1-gex-r2.tar.gz
> % cd grads-1.9.0-rc1-gex-rc2/extensions
>
>
> Make a directory for your function and copy some basic files in it:
>
>
> % mkdir floor
> % cp hello/GNUmakefile floor
>
>
> Now place your floor.c function in this new directory, and add a file named
> "floor.udxt.in" with something like:
>
>
> #  Type       Name            Function                 Library
> # ------  ---------------  ----------------
>  --------------------------------
>    udf        floor          gaudf         floor.gex. at DLLEXT@
>
>
>
> Then build your function
>
>
> % cd floor
> % make
>
>
> This should create floor.gex.so (or floor.gex.dylib on Mac OS X) and
> floor.udxt . It is just a bit more complicated to do this on Windows but it
> can be done.
>
>
> To test it run grads from this directory and
>
>
> % export GAUDXT="./floor.udxt"
> % export LD_LIBRARY_PATH=`pwd`
> % gradsnc -l
> ga-> open something
> ga-> q udft
> (should show your floor function)
> ga-> display floor(whatever)
> (it should work)
>
>
> Once you are convinced that it works install it. Add the contents of
> floor.udxt to your main udxt file and put floor.gex.so alongside your
> other extensions. That is it.
>
>
> Additional information about the opengrads extensions are here:
>
>
>
>       http://opengrads.org/wiki/index.php?title=User_Defined_Extensions
>
>
>
> VERY IMPORTANT: This is the procedure in v1.9.0-rc1 and details will very
> likely change for grads v2. So, any function developed for v1.9 will need to
> be ported to v2.0. Therefore, unless you need something that cannot wait,
> there is no much point in developing new functions for v1.9.
>
>
>    Good Luck,
>
>
>       Arlindo
>
>
> --
> Arlindo da Silva
> dasilva at alum.mit.edu
>
>
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