| surface fittin [message #42988] |
Fri, 04 March 2005 05:45 |
Tal Feingersh
Messages: 2
Registered: November 2002
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Junior Member |
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hello,
i have a certain physical phenomenon that i visualize in IDL with a surface
(or image), where x and y dimensions are the explaning independent variables
and the z dimension is the dependent variable. this surface has usually a
rather smooth variation and its icludes a "topography" of "hills" and
"valleys".
i also want to save a formal definition of this surface (its polynomial
coefficients) so i can use it for further analysis later on.
i worked with SFIT for that and used a 6th order polynomial which does a
good job (when looking at the output image it creates). however, when trying
to reconstruct that image that i see, by using the required x, y and the
coefficients, the resulting surface is far from being similar to what the
surface really is. i managed to fully and exactly reconstruct a 3x3
Gaussian. so i know that i read the KX coefficients correctly. i also
defined my x and y variables correctly (100% sure). but is doesn't work for
my 72x15 pixels surface. KX is a floating point output. it could be that
when saved as double precision, results will be better. but there is no
keyword for that.
any other ideas?
thanks in advance.
----------
Tal
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