On 2005-01-02,

http://www.velocityreviews.com/forums/(E-Mail Removed) <(E-Mail Removed)> wrote:

>>However, I can't find anything usable from Python, and my

>>Fortram skills are pretty rusty. I tried SciPy, but it's spline

>>fitting module doesn't work at all for my data. I've found

>>mentions of a Python port NURBS toolbox, but all the links I

>>can find are broken.

>

> NURBS is available in Matlab and Scilab at

> http://www.aria.uklinux.net/nurbs.php3 , and translating to

> Python with Numeric/Numarray should not be too hard.
Right. It says there's a Python module for the NURBS toolkit,

but there's nothing about NURBS on the page to which the link

points. Googling for Python and NURBS toolkit doesn't find

anything else.

> If you are trying to fit z = f(x,y) without having a particular

> functional form in mind, you can apply a nonparametric regression

> technique. One of the easiest approaches to code is Nadaraya-Watson

> kernel regression -- see for example

> http://www.quantlet.com/mdstat/scrip...tmlnode24.html ,

> equation 4.68,
Well, I can see it, but that's about it...

> where a Gaussian kernel can be used for K. PyML at

> http://pyml.sourceforge.net/doc/tutorial/tutorial.html may

> implement this (I have not tried it).
Thanks, I'll take a look.

> LIBSVM at http://www.csie.ntu.edu.tw/~cjlin/libsvm/ has a

> Python interface for Support Vector Machines, a fairly popular

> and recent flexible regression method.
I'll give that a look also.

One of the important considerations is the efficiency of

evaluating the approximating function (calculating z given x

and y). That code is going to be running on a rather slow

processor w/o floating point HW, and if the evaluation takes

more than about 40ms, I'm going to have problems. The

evaluating the spline surface produced by scipy's FITPACK

wrapper was fast enough, but I had to force the scattered data

onto a grid (which introduced errors), and then the spline

surfaces generated were wildly unstable between the grid

points.

--

Grant Edwards grante Yow! The Korean War must

at have been fun.

visi.com