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MathGroup Archive 1999

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Re: searchforperiod

  • To: mathgroup at
  • Subject: [mg19866] Re: searchforperiod
  • From: John Tanner <john at>
  • Date: Sun, 19 Sep 1999 01:20:48 -0400
  • Organization: Peace with the World
  • References: <7rnkao$>
  • Sender: owner-wri-mathgroup at

There is a very nice illustration of "Spectral Analysis of Irregularly
Sampled Data" in the In And Out section of Mathematica Journal vol 7
issue 1 (winter 1997), with a real case of pulsar data with not only
irregular spacing but also large gaps.  

Unfortunately this issue was immediately prior to the long-drawn-out
break in publication of this extremely useful publication.  The later
issues (vol 6 and vol 7 no 1) have not yet reached MathSource, even
though vol 7 no. 2 is directly available on the Web page

I am not sure what the copyright status is so I will not will not post

Good luck.

In article <7rnkao$elp at>, Andre Hautot <ahautot at>
>Is Mathematica able to solve the following kind of problem?
>I have computed the time evolution of a certain quantity, say rmod, (the
>details of the physical problem which leads to them are unimportant).
>The results are contained in a list like this :
>To fix the ideas here is the beginning of a typical list :
>The rmod-values increase during 35 steps and they decrease during the 35
>next steps, returning near the initial value of one after 70 steps, and
>so on. Similarly, the time spacing increases during 35 steps, decreases
>during the 35 next steps and so on.
>The coordinates are known with arbitrary high precision (50 figures for
>example or more if you need)
>The graph of rmod versus t is obtained, as usual, by
>It seems to be periodic. How can verify such a conjecture and obtain a
>high precision value for the period?
>Since 70 points are contained within a period one understands that 5000
>points approximatively correspond to 71 full periods. Note however, and
>this seems to be the main difficulty, that the time abscissas of the
>points are not equally spaced. Otherwise discrete Fourier transform
>should be convenient.
>The classical litterature generally deals with equally spaced abscissas.
>Has somebody heard of a generalized algorithm?
>Of course I could interpolate the function, rmod versus t, but the
>accuracy of the period obtained in that way is ridicoulusly low compared
>to the, say 50 figures, injected in the data. Thanks in advance.
>Andre Hautot
>Universite de Liege
>Physique Generale
>Institut de Physique-B5
>4000 Liege
>Tel: 32 4 366 36 21
>Fax: 32 4 366 45 16
>Email: ahautot at

  from -   John Tanner                 home -  john at
  mantra - curse Microsoft, curse...   work -  john.tanner at
I hate this 'orrible computer,  I really ought to sell it:
It never does what I want,      but only what I tell it.

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