Hi Valery,
I have a function called curvefit() which can be used for interpolation and the resulting curve can be differentiated. You can get
it from this link below, it is part of pw.mac. I am working on faster ways to do this but for now it is not lightning fast. Also
curvefit() is experimental and does not always work perfectly. If you use a degree of 7 or so it should work okay but that depends
on the points being fitted probably.
Rich
http://home.comcast.net/~rvh2007/site/?/page/Pw.mac_2.2/
----- Original Message -----
From: "Valery Pipin" <pip at iszf.irk.ru>
To: "Robert Dodier" <robert.dodier at gmail.com>
Cc: <maxima at math.utexas.edu>
Sent: Tuesday, December 09, 2008 10:45 PM
Subject: Re: [Maxima] approximating a curve
On Tue, 9 Dec 2008 08:21:31 -0700
Robert Dodier wrote:
> On 12/8/08, Valery Pipin wrote:
>
> > real life example. Using the Peter's Eggleton stellar evolution code
> > I've got a table of the stellar interior parameters for the Brown
> > Dwarf (0.2 M_sun, 0.006 L_sun). The parameters are pressure,
> > temperature, luminosity, density and etc.. . Now I want to use
> > their functional form in my dynamo model. The best way is to get the
> > Chebyshev approximations to them. I do as follows,
> > 1) read the table to maxima
> > 2) find the spline interpolation
> > 3) find the Chebyshev approximations
>
> Hey, that rocks. But I don't quite understand what's going on here.
> Why is there both a cubic spline and a Chebyshev approximation?
Agree, it is not an ideal way.
The problem is that I can not use the given spline approximations to
differentiate them further. I have use it to interpolate the table to
the Chebyshev nodes. It was a fast solution (in sense, that everything
is at hands).
best regards
Valery
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