contouring weirdness with FillValues

From: David Reusch <dbr_at_nyahnyahspammersnyahnyah>
Date: Sun, 28 Sep 2008 21:11:44 -0400


I have come across some "weirdness" in NCL contouring that I have not
been able to resolve and was hoping for some help. The attached figures
show what I hope to produce and what I'm getting for specific datasets
that have _FillValue data in them. In the "bad_plot" image, the central
unfilled area is being plotted correctly as it represents _FillValue
data. The areas "above" and "below" are also handled correctly. It's
only the areas to each side that go crazy with contours (and I get the
same result without the color fill).

I am building these netCDF files myself using Python/pycdf (script
cod_to_nc, in the tar file) and have not been able to find any oddities
in these files that would explain the contouring madness. I have also
looked at the data extensively as the NCL script is running with no
insights. At this point it seems like something amiss in NCL -- though
this is my first real experience using files with FillValues so I can't
rule out entirely that it's my fault.

The link below is to a tgz-file with the script, data and larger (4x3
panels) examples of my output. The script (plot_var.ncl) takes a netCDF
file as input and produces a postscript output. To reproduce the files
that have these sample images, use these commands respectively:
ncl 'var="h500z"' plot_var.ncl
ncl 'var="h700z_msk"' plot_var.ncl

I am using NCL 5.0.0 and seeing the same results on both Mac OS 10.5.5
and 10.4.11.

Script, data, output here:

Thanks for your time,
Dave Reusch

517 Deike Building
Earth & Environmental Systems Institute
Penn State University
University Park, PA 16802

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Received on Sun Sep 28 2008 - 19:11:44 MDT

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