- To: mathgroup at smc.vnet.net
- Subject: [mg19866] Re: searchforperiod
- From: John Tanner <john at janacek.demon.co.uk>
- Date: Sun, 19 Sep 1999 01:20:48 -0400
- Organization: Peace with the World
- References: <email@example.com>
- Sender: owner-wri-mathgroup at wolfram.com
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
In article <7rnkao$elp at smc.vnet.net>, Andre Hautot <ahautot at ulg.ac.be>
>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.
>Universite de Liege
>Institut de Physique-B5
>Tel: 32 4 366 36 21
>Fax: 32 4 366 45 16
>Email: ahautot at ulg.ac.be
from - John Tanner home - john at janacek.demon.co.uk
mantra - curse Microsoft, curse... work - john.tanner at gecm.com
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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