[AstroPy] ffa in python

[Peter Williams]

To search for periodicity in the arrival times of discrete events,
rather than continuously sampled data, the Rayleigh test is a good
place to start:

http://adsabs.harvard.edu/abs/1994MNRAS.268..709B
http://www.astro.ubc.ca/people/jvw/ASTROSTATS/Answers/Chap9/chapter%209
%20rayleigh%20test.pdf

Peter

On Tue, 2015-06-09 at 09:21 -0700, R Schumacher wrote:
> I've only a cursory knowledge of FFA, but FFT assumes sinusoidal data 
> (or sums of) and so may not best represent periodic pulses in, say, 
> single ended data acquisition, or swept signals etc
> 
> FFA is supposed to look for regularity in pulses
> http://en.wikipedia.org/wiki/Talk%3AFast_folding_algorithm
> Being an amateur astronomer I searched your use case
> https://books.google.com/books?id=OZ8tdN6qJcsC&pg=PA151&lpg=PA151&dq=
> fast+folding+algorithm&source=bl&ots=mwe0QvaHU5&sig=Xg1Kwad46yC_BMxyK
> u_GR37LaFA&hl=en&sa=X&ei=EhF3VYudBojiUeiogvAH&ved=0CDAQ6AEwBg
> 
> 
> - Ray
> 
> 
> At 08:33 AM 6/9/2015, you wrote:
> > Good ! Thanks !
> > Any comment about the comparison between ffa and fft?
> > Hang
> > 
> > On Tue, Jun 9, 2015 at 11:18 PM, R Schumacher <rays at blue-cove.com> 
> > wrote:
> > https://github.com/petigura/FFA/blob/master/FFA.py
> > 
> > 
> > 
> > At 07:49 AM 6/9/2015, Anne Archibald wrote:
> > > I don't think there's a general FFA algorithm anywhere, though 
> > > Vlad Kondratiev wrote a tool for applying the FFA to radio data, 
> > > and I have some python code lying around somewhere. If you're 
> > > searching for periodicities, the standard procedure is to search 
> > > an FFT with incoherent harmonic summing; there are some pulsar 
> > > searching tools that will do it (PRESTO, for example) quickly and 
> > > efficiently. If you only have a handful of photons, or a modest 
> > > number of periods to search, there are direct approaches that are 
> > > more sensitive. If you have really a long time series, there is a 
> > > trick where you do an FFT on the pairwise differences of photon 
> > > arrival times. 
> > > 
> > > In short, there are a whole range of procedures for searching for 
> > > periodicity in data. Can you be a little more specific about the 
> > > problem you are trying to solve?
> > > 
> > > Anne
> > > 
> > > On Tue, Jun 9, 2015 at 4:44 PM gonghang.naoc <
> > > ghang.naoc at gmail.com> wrote:
> > > Hi all,
> > > Is there any python resource about fast folding algorithm?  I 
> > > have a series of arrival times for a lot of photons. I need to do 
> > > some periodical test, but do not know how to start.
> > > Thank you.
> > > best
> > > Hang
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