| Re: Co-Linear Contour Points [message #36463 is a reply to message #36370] |
Wed, 17 September 2003 06:54   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Nate Doyle writes:
> I'm trying to plot a contour and am getting an error that tells me my
> points are co-linear. I'm not exactly sure what's going on so I
> figured I'd appeal to you people.
I see you are not being flooded with answers. :-)
That's probably because the universe of "what's going on"
for this particular question is quite a bit larger than
it is for most typical answers in this newsgroup.
Basically, your data is co-linear, but you already
knew that. :-)
The question is: why? And that is hard to answer.
Maybe your data really is in a straight line. Have
you looked at it in some other way? Maybe you have
two points that are identical. Have you checked for
that?
The CONTOUR command requires gridded data. Your
data is being gridded by TRIANGULATE and TRIGRID.
Sometimes this kind of error message is created
when the /SPHERICAL keyword is used on TRIGRID.
(I don't know why.) I wonder if this keyword gets
set when you are overplotting on a map projection.
(I don't know how to test this.)
In any case, I would try gridding the data myself.
First with the TRIANGULATE/TRIGRID method, and then,
if necessary, with GRIDDATA.
Another way to (sometimes) shake this problem loose
is to add a tiny bit of random location data to your
coordinates.
I don't know if one or any of these suggestions
might help. But maybe you will get a couple of ideas.
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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