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- Path: sparky!uunet!dtix!darwin.sura.net!uvaarpa!concert!borg!vivaldi!frederic
- From: frederic@vivaldi.cs.unc.edu (Robin Fredericksen)
- Newsgroups: sci.math.symbolic
- Subject: Re: Using Mathematica to fit a surface to data(+ another Q?)
- Keywords: Mathematica, curve fit, surface plot
- Message-ID: <18476@borg.cs.unc.edu>
- Date: 19 Dec 92 18:15:51 GMT
- References: <1gst2gINNfsk@tamsun.tamu.edu>
- Sender: news@cs.unc.edu
- Organization: The University of North Carolina at Chapel Hill
- Lines: 74
-
- In article <1gst2gINNfsk@tamsun.tamu.edu> bryan@kolsky.tamu.edu (Bryan Milligan) writes:
- >
- > Is there a routine in Mathematica to fit a surface to a set of
- >(x,y,z) data? I have some FEM data that I need to differenciate, and I
- >would like to fit a polynomial curve to the data and differenciate that
- >as opposed to numerically differenciating the data itself.
- >
- >--
- >
- >Bryan Milligan
- >Department of Aerospace Engineering
- >Texas A&M University
- >bryan@kolsky.tamu.edu (NeXT Mail accepted)
-
-
- I use the Interpolate function to do this. The data points have
- to be on a grid in that the sample set must be complete on the
- axis but the sample grid can be irregular. There can be any
- (unlimited?) number of dimensions to the data, and you can
- (with the caveat that I describe below in my own question)
- specify the order of the polynomial used for interpolation.
- I don't know whether you can use other functions (e.g. sinusoids,
- etc.)
-
- Now, my problem is somewhat different, and has to do with the
- Interpoate[] function, so I will ask the NET since it is directly
- relevant to you if you would like to use it. :-)
-
- ====NEW BUT RELATED QUESTION====
- I am using Mathematica (on a Mac) for reading in a data file
- with points with a non-square (non-regularly spaced) grid of points.
-
- (i.e. sample points that look like)
-
- 0 0 0 0
- 0 0 0 0
-
- 0 0 0 0
-
-
-
- 0 0 0 0
-
-
-
-
-
- 0 0 0 0
-
-
-
- I am using the Interpolate[] function that mathematica offers
-
- Function = Interpolate[ <datalist>, InterpolationOrder->1]
-
-
- As I understand the manual, this should create a function which
- provides as output the above data with linear interpolation between
- the points. However the output that I get from this is definately
- NOT a linear interpolation, but something that looks quadratic.
-
- Can anyone tell me how to fix this? Is there a simple work-around?
-
- Please email responses to frederic@cs.unc.edu
- as well posting, if possible.
-
- Thanks.
- Eric Fredericksen
- frederic@cs.unc.edu
- --
- -------------------------------------------------------------------------------
- Eric Fredericksen : Insert amazingly funny or enlightening quote
- frederic@cs.unc.edu : in this space here.
- I don't need a disclaimer, I'm a graduate student so no one cares what I say...
-