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Re: minimax polynomial determination

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115819] Re: minimax polynomial determination
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Fri, 21 Jan 2011 04:34:37 -0500 (EST)
  • References: <ih3r5c$b8n$1@smc.vnet.net>

On Jan 18, 2:48 am, Leslaw Bieniasz <nbbie... at cyf-kr.edu.pl> wrote:
> Hi,
>
> I need to determine minimax polynomial approximations to a certain
> function computed using MATHEMATICA. Unfortunately it is not possible
> to calculate exact derivatives of the function. Is there any way to
> use the MiniMaxApproximation[] algorithm with numerically approximated
> derivatives? I would appreciate an example.
>
> Leslaw

Further to my first post, I seem to remember that, when I've done
this sort of thing in the past, I've had better luck with FindRoot
than with FindMinimum as the outer function. Instead of minimizing
the max of the absolute values of the local extrema of the error
curve, set the sums of adjacent pairs of signed local extrema all
to zero. The inner calls would be to a "findExtremum", which would
return a local min or max.


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