FW: one contour level

[Dave Allured]

Lynette Bettio wrote:

>Hi,
>hoping this is an easy question.
>I have a script with which I read in a data file and graph results. In
>this script I have each contour level set and an rgb colour for that
>level.  Normally this works fine, data is read in and graphed, and
>using cbarn the full colour range is displayed, even if the end
>contours aren't reached. However, I recently put some data through and
>the script produced a blank map - no shading or contour bar. I checked
>the original file and where there weren't special characters the input
>was all the same number (1). So I'm guessing from that and the error
>messages that grads was unable to shade without at least two levels.
>This number is in the range of my set contour levels (and a specified
>contour level) and I would like to be able to display it with the
>whole map (except for spec char areas) shaded the colour for the level
>specified and display some form of cbarn underneath. I would appreciate
>any help in this matter. Thankyou.
>Regards,
>Lyn
>
>
Lyn,

This is similar to the problem that I reported to Grads Users Group on
2004-feb-18.  For the full discussion, please check the list archives
for the thread "Display constant field without blanking":

  http://list.cineca.it/archives/gradsusr.html

I suggested the following workaround.  Tweak one of the corner points
slightly, to force the contouring algorithm to generate a plot rather
than an error condition.  In my experience, the resulting glitch in the
output sequence is almost unnoticeable.  HTH.

--Dave A.
CDC/NOAA/CIRES