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