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MathGroup Archive 2003

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Re: Interpolation over an irregular surface

  • To: mathgroup at
  • Subject: [mg39247] Re: Interpolation over an irregular surface
  • From: Jens-Peer Kuska <kuska at>
  • Date: Thu, 6 Feb 2003 03:06:51 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <b1q6o9$347$>
  • Reply-to: kuska at
  • Sender: owner-wri-mathgroup at


the easy way would be to edit the file
and return the adjacence information (as written
in the package comments).

If you don't like this you can make a loop over all
triangles, and append the point list in the triangle
to the adjacence list of every vertex in the triangle,
finaly build the Union[] of the adjacence list for every
vertex and remove the index k of the adjacence list for
vertex k.


Jacob Rome wrote:
> I'm trying to map (interpolate) temperatures from one 2D set of points
> to another for a finite element application.  The initial set of
> points is {x1,y1,t1} and the second set is {X1,Y1,T1}, and I know all
> the values except for T1. I have connectivity data for the new mesh
> {X1,Y1}, but not for the original mesh (x1,y1).
> I have downloaded the ExtendGraphics package, and it has a functions
> (TriangularInterpolate) which should do exactly what I need. No error
> is given when I initially use it
> (interpFunc=TriangularInterpolate[nodeTemp], where nodeTemp is a
> 3-column matrix). However, when I invoke it again (interpFunc[x1,y1]),
> I get a series of errors, primarily about reaching the recursion or
> iteration limits. Could this have to do with the size of the initial
> matrix (~15,000 sets of data), or is there a different problem? It
> only seems to work correctly when the point is outside of the initial
> region, or if all the nearest nodes have the same temperature.
> After this setback, I planned to use the Delaunay function in the same
> package to help write my own interpolation routine. Using this
> function should return three sets of data: the Convex Hull, Adjacency
> Matrix and the Triangles. However, it appears that only the Convex
> Hull and the Triangles are returned; to effectively write an
> interpolation routine, the Adjacency Matrix is crucial. How can I get
> this data from the Delaunay function?
> Any advice on solving this problem is greatly appreciated, whether you
> can suggest an alternative approach or provide a means to use these
> functions more effectively. Thank you.

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