Re: Missing values - additional comments

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Mon Aug 06 2012 - 09:15:13 MDT

Hi Lena,

Is there a reason you're using GPL over Autograph?

Any calls directly to GKS routines like GPL do not recognize missing values, unfortunately.
You would need to loop over the values yourself and test for when you encounter a missing value.

NCAR Graphics is considered dated, and we recommend people move to NCL if possible.
With NCL, you will be able to easily read in a multitude of data formats, like NetCDF,
HDF, and GRIB, do some calculations, and generate a plot.

NCL has routines similar to GPL, called gsn_polyline (for drawing on an existing plot) and
gsn_polyline_ndc (for drawing on a canvas, like GPL). These routines do recognize missing values.

See the attached NCL script. If you have NCL, you should be able to run it with:

    ncl msg.ncl

You need to click on the X11 window with your left mouse button to advance each frame.

Let me know if you want to look some more into NCL, and I'll point you to some examples. You
can also browse the whole page at:

http://www.ncl.ucar.edu/Applications/

--Mary

On Aug 6, 2012, at 8:04 AM, Lena Iredell wrote:

> I recently posted the following message, but forgot to include that I am
> using GKS routines with the programs written in Fortran.
>
> I would like to plot a line plot, using either gpl, curve, or curved. My
> data has missing values, which I would like displayed as gaps in the
> line. How do I pass my missing value to the NCAR graphic programs so the
> routines will ignore plotting the line segment at that point?
>
> I see in the Autograph documentation that the special values 'null/1'
> and 'null/2' are available for use that seem to do this. Will setting
> them work for gpl and curve as well? If so how do I actually set them?
> What routines do I pass these function codes to? I am having some
> difficulty finding the exact documentation on your web site that tells
> how actually set and use these special values.
>
> Thanks for any help you can provide!
>
> Sincerely,
>
> Lena
>
>
> --
> Lena Iredell
> SAIC
> NASA Goddard Space Flight Center
> Code 610
> Phone: 301.286.9773
>
> _______________________________________________
> ncarg-talk mailing list
> ncarg-talk@ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/ncarg-talk

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Received on Mon Aug 6 09:15:31 2012

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