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MathGroup Archive 1998

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Multidimensional Interpolation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg12766] Multidimensional Interpolation
  • From: Sean Ross <seanross at worldnet.att.net>
  • Date: Wed, 10 Jun 1998 03:04:24 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

While attempting to make some nice 3D plots of {x,y,z} data for a
friend, I ran into the strangest behavior I am hoping someone can shed
light on.  First, some background:

Interpolation[{{x1,y1,f1},{x2,y2,f2},...}]

usually requires a square number of data points.  If you give it 48 data
points, it will come back with an error message saying that the number
of points n in dimension 2 is not 7, since somehow Interpolation has
decided that there ought to be 49 points in the set.

The data supplied to me by my friend had 441 data points, which is 21^2.
Interpolation came back and told me that the number of points in
dimension 2 was not 2 ???!, so it couldn't do anything.  As a test, I
generated sample data with Table that also had 441 {x,y,z} data points
of the same format and Interpolation had no problem with the canned
data, but 8 sets of real data supplied by my friend gave the same
problem, where Interpolation thought that there should be 2^2 rather
than 21^2 data points in the set.

Can anyone shed some light on how Interpolation determines its subsets
and what I might look for in the data set?  Perhaps I might re-order
the data somehow if I understood what Interpolation was looking for. 
If anyone is interested, I can send you the original data.

Thanks


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