Re: Expl. form of Interpolation[] ?

*To*: mathgroup at smc.vnet.net*Subject*: [mg3680] Re: Expl. form of Interpolation[] ?*From*: Robert Knapp <rknapp>*Date*: Fri, 5 Apr 1996 02:52:45 -0500*Organization*: Wolfram Research, Inc.*Sender*: owner-wri-mathgroup at wolfram.com

Manfred Krafczyk wrote: > > Dear All, > given a set of points in list={y1,y2,...,yk} one can use > f=Interpolation[list] to get an implicit interpolation function > which can be plotted etc., but I did not find out how > to get the explicit polynomial f[x] which is implicitely generated > and used by calling f[x] (i.e. the coefficients > of the powers in 'x') in order to port this algebraic > expression into a C code for further use. > Any ideas welcome (preferably e-mail), > Thanks in advance > Manfred Krafczyk The InterpolatingFunction produced by Interpolation does not use a single polynomial. It uses a piecewise (default 3rd order) polynomial approximation. It is possible to obtain the coefficients using the InterpolatingPolynomial function. Since InterpolatingPolynomial does not use a piecewise approximation, if you want a piecewise approximation, it will be necessary to partition you interval in sections: you can use Partition and Map to do this realtively easily. -- Rob Knapp Wolfram Research, Inc. http://www.wri.com/~rknapp ==== [MESSAGE SEPARATOR] ====