[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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