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Chebyshev approximations.
- From: Andrea Riciputi <ariciputi at pito dot com>
- To: Gnu Scientific Library <gsl-discuss at sources dot redhat dot com>
- Date: Wed, 4 Jun 2003 16:16:45 +0200
- Subject: Chebyshev approximations.
Reading the reference manual's chapter about Chebyshev approximation
it's not clear (at least to me) how the c_n are defined. In particular
I've found out that I've to double all the coefficients I've calculated
by my own, in order to get gsl_cheb_eval to work properly.
My c_n definition is:
c_n = k \int{0}{\pi} f(x) \cos(n x) dx
where k = 2/pi if n != 0 and k = 1/pi if n == 0. Given these
definitions the series expansion is:
f(x) = \sum{k = 0}{N} c_k cos(k x)
Where am I wrong?
Thanks,
Andrea.
---
Andrea Riciputi
"Science is like sex: sometimes something useful comes out,
but that is not the reason we are doing it" -- (Richard Feynman)