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MathGroup Archive 2007

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Re: Optimisation of FourierCoefficients

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75232] Re: [mg75198] Optimisation of FourierCoefficients
  • From: Sseziwa Mukasa <mukasa at jeol.com>
  • Date: Sat, 21 Apr 2007 23:10:16 -0400 (EDT)
  • References: <200704200437.AAA00850@smc.vnet.net>

On Apr 20, 2007, at 12:37 AM, Edmund wrote:

> I want to find the minimum of a Fourier-Coefficient as a function  
> of the
> input values.
>
> FindMinimum[Abs[Fourier[{ y, 1}][[1]]], {y, 2}]
>
> The actual problem is a little more complicated, but even this simple
> statements gives the error messages I can't understand.
>
> Fourier::fftl: Argument {y, 1} is not a non-empty list or  
> rectangular array
> \
> of numeric quantities.
>
>
> Any suggestion ?

Fourier only works on numeric data hence the message when you try to  
compute the transform of {y,1}.  FindMinimum works on symbolic  
expressions so fixing your expression to evaluate y first would be  
problematic since there will be no y in the result and FindMinimum  
would be unable to compute the gradient.  You need to compute the  
general form of your Fourier Coefficient first, then find the minimum  
of that function,

Regards,

Ssezi


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