[nSLUG] Possibly ignorant quest for simple FFT app
Vlado Keselj
vlado at cs.dal.ca
Thu Jul 11 06:05:04 ADT 2013
I do not use FFT in practice, but if I were I would probably try:
1. GNU Scientificy Library -- free, open-source, likely efficient and
mature
http://www.gnu.org/software/gsl/manual/html_node/Fast-Fourier-Transforms.html
2. MATLAB - commercial, probably efficient and mature implementation
http://www.mathworks.com/help/matlab/ref/fft.html
3. Octave -- free, open-source software similar to Matlab
http://www.gnu.org/software/octave/doc/interpreter/Signal-Processing.html
4. Math::FFT Perl module -- free, open-source, seems efficient (based on a
C implementation)
http://search.cpan.org/~rkobes/Math-FFT-1.28/FFT.pm
There seems to be other implementations in Perl too. I am sure there must
be at least one in Python.
Regards,
Vlado
On Thu, 11 Jul 2013, Mike Spencer wrote:
>
> Summary: Looking for Fourier software simpleminded enough for me to be
> able to use it.
>
> I have a basic, possibly horribly distorted, idea of what a Fourier
> transform does: You can make believe that:
>
> + any list of numbers are the amplitudes of one cycle of a
> hypothetical periodic function for even-spaced values of t,
> or that
>
> + any list of pairs of numbers are the t/amplitude values for
> one cycle of a hypothetical periodic function.
>
> And Fourier's insight says that any periodic function can be
> represented as an infinite series of sums, vaguely like:
>
> inf
> SIGMA A sin(nt) + B cos(nt) [where A & B are subscripted with n]
> n=1
>
> Yeah... [1]
>
> I'd like a simple command line program that will take an arbitrary
> array of numbers or x/y number pairs and return the A & B coefficients
> up to some modest max value for n.
>
> What I find on the net is one of:
>
> + FFT libraries for which I have to write surrounding code.
>
> + Interactive apps for serious DSP guys.
>
> + Apps for serious math weenies.
>
> all of which seem to start out assuming I know waayyy more than I do
> (viz. very little) about the subject and don't promise to give me the
> simple results sought.
>
> Purpose is to look for frequency patterns (if any) in putative random
> numbers and also -- even more frivolously -- in the recordings made
> from the mouse exercise-wheel tachometer. [2]
>
> I recall seeing graphic rendering of data from (what I took to be)
> such a Fourier program on the screen of a guy who was doing hard-core
> random number research for crypto. I've lost track of him.
>
>
> Maybe I'm so ignorant in this area that this is all too misguided for
> a meaningful reply. In that case you can just treat this as idle
> entertainment on a slow day for the NSLUG list.
>
>
> - Mike
>
>
> [1] ...the real equation with discussion is in my old calculus
> textbook. I'm weak on math and it doesn't get better with age.
> Not looking for a tutorial on Fourier math or FFT code.
>
> [2] Our mouse slacked off all winter but resumed using the wheel in
> the spring and I've logged over 30 evenings of running. Record is
> 16,000+ turns of the wheel or about 4.8 miles in one evening.
> Visualizing the data requires an image 480x24000 pixels which
> gnuplot does nery nicely. :-)
>
> --
> Michael Spencer Nova Scotia, Canada .~.
> /V\
> mspencer at tallships.ca /( )\
> http://home.tallships.ca/mspencer/ ^^-^^
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