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Re: How to handle fft of initial condition?
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From: |
Miroslaw Kwasniak |
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Subject: |
Re: How to handle fft of initial condition? |
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Date: |
Tue, 19 May 2009 10:32:31 +0200 |
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User-agent: |
Mutt/1.5.9i |
On Mon, May 18, 2009 at 08:22:12AM -0700, John B. Thoo wrote:
> My question is this: If I let [u0^] = fft (u0), how do I match a
> negative index k when Octave begins with k = 1? E.g., if k = -3,
I you use U0=fftshit(fft(u0)) then index c=floor(length(U0)/2)+1
gives position of zero frequency in spectrum.
Then your u0^(k) is equal U0(c+k).