Ticket #854 (closed: fixed)

Opened 11 years ago

Last modified 5 years ago

FFT variants - smoothing

Reported by: Nick Draper Owned by: Roman Tolchenov
Priority: major Milestone: Iteration 20
Component: Keywords:
Cc: Blocked By:
Blocking: Tester:

Description

I use FFT for smoothing & derivatives and found them better than other methods. Smoothing The principle is that the data is transformed, truncated to remove noisy points at high x and back transformed. The simple version just truncates to 1/n of the range – this corresponds to n point smoothing. The sophisticated version uses the Weiner filter which chooses the truncation point according to the statistical errors. I found this very reliable for data with peaks. Derivatives By swapping the real & imaginary parts of the transform & back transforming you can get the derivatives. Then by truncating, you can get smoothed versions. Versions of these would be useful if they do not already exist. Sp

Change History

comment:1 Changed 11 years ago by Nick Draper

  • Owner set to Roman Tolchenov

comment:2 Changed 11 years ago by Roman Tolchenov

(In [3213]) Added FFTSmooth algorithm with a couple of simple filters. re #854

comment:3 Changed 11 years ago by Roman Tolchenov

(In [3239]) Improved FFTSmooth. re #854

comment:4 Changed 11 years ago by Roman Tolchenov

(In [3245]) Added RealFFT algorithm and changed FFTSmooth to use it. re #854

comment:5 Changed 11 years ago by Roman Tolchenov

  • Status changed from new to closed
  • Resolution set to fixed

Needs more filters (e.g. Wiener)

comment:6 Changed 11 years ago by Nick Draper

  • Status changed from closed to reopened
  • Resolution fixed deleted

Algorithm appears to do nothing if the workspace does not have regular bins. Output a warning level message to the log and update the wiki documentation to explain that the input must have regular binning.

Also mark the truncation filter as not implemented yet in the documentation.

comment:7 Changed 11 years ago by Roman Tolchenov

  • Status changed from reopened to accepted

comment:8 Changed 11 years ago by Roman Tolchenov

  • Status changed from accepted to testing
  • Resolution set to fixed

comment:9 Changed 11 years ago by Russell Taylor

  • Status changed from testing to closed

comment:10 Changed 5 years ago by Stuart Campbell

This ticket has been transferred to github issue 1702

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