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Re: finding approximate 'least common factor'


From: Przemek Klosowski
Subject: Re: finding approximate 'least common factor'
Date: Wed, 25 May 2011 10:08:28 -0400
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On 05/25/2011 07:05 AM, Francesco Potortì wrote:
I have numbers which are approximately (but not exactly) an integer
number of some basic quantity. How would you estimate that basic
quantum? For instance, if the data is:

All I could come up with is to look at all the candidates (s) and
plot the sum of squares (d) of the integer quotient residuals (c)
against the value of the candidates...

Can anyone think of a more precise numerical algorithm?

Might try some sort of discrete Fourier transform, where the numbers
represent the x values and the count of values at each x represents an
impulse function of that amplitude.

Right, it could be seen as an instance of the classic problem of "pitch
detection" or "fundamental frequency estimation" of a sampled sound.

OK, but for sound you'd typically have O(1e5) data points (couple of seconds of 44kHz samples), whereas here I have a couple dozen maybe, and the FFT is mighty noisy and boundary conditions are a murder. Perhaps there are some filtering techniques that would help. Are there any good 'pitch detection' Octave/Matlab codes around?
that


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