Re: Bug resampling field with Irregular2DSet to Linear2DSet

  • To: Ian Graham <ian@xxxxxxxxxx>
  • Subject: Re: Bug resampling field with Irregular2DSet to Linear2DSet
  • From: Bill Hibbard <billh@xxxxxxxxxxxxx>
  • Date: Tue, 29 Apr 2003 05:21:50 -0500 (CDT)
Hi Ian,

We will need a test case for debugging this. But first a
couple questions:

1. Are you generating your own topology passed to
DelaunayCustom, or are you letting the system compute
its own?

2. When you offset X and y values, do you do that before
you or the system computes the topology, or do you compute
the topology and then offset the x and y values?

In any case, we will need a program, any necessary data
files, and instructions for compiling and running the

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738

On Mon, 28 Apr 2003, Ian Graham wrote:

> I'm trying to resample a field for which the domain is an x/y tuple defined
> by an Irregular2DSet, and the range is a simple RealType.  Basically I want
> to make an interpolated image out of a scatter plot, so I'm resampling my
> field using the points of a Linear2DSet.
> Any simple examples I create seem to work fine, so I'm unable to give a code
> example that demonstrates the problem, but my symptom is that large portions
> of my resampled field are filled with NaN.  If I offset my x values so they
> are all positive, then missing horizontal strips are resampled properly.  If
> I offset my y values so they are all positive, then the missing top
> portion(which is sometimes everything) of the data gets displayed properly.
> I find the resampling code pretty intimidating, but I'm hoping a developer
> can look through it and pick out the problem.  If not, then I'll have to
> send my whole set of data(2900 points), or the Irregular2DSet created by
> them.  I'm pretty sure the triangulation is OK, because a plot of the field
> whose domain is the irregular set itself looks reasonable, and I can easily
> evaluate the field for any pair of coordinates OK.
> I've even tried to create an equally complex irregular set from random
> points, and I still can't recreate the problem except with my specific set
> of points.
> Anyway, I put some quick screen-dumps illustrating the problems at
> ml
> Thanks for any help resolving this!
> Ian

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