Discrete FFT in basic

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2 total messages Started by Ames Grisanti Mon, 16 Nov 1992 05:05

#293

Author: Ames Grisanti
Date: Mon, 16 Nov 1992 05:05

16 lines
1011 bytes

Hello,

Does anyone out there have basic (QB or GW) source code for a discrete
fast fourier transform? Or know where I might get one?

Thanks

Ames Grisanti

University of North Dakota
Energy and Environmental Research Center
[grisanti@plains.NoDak.edu      --         Internet]
[grisanti@plains or ndsuvax     --         Bitnet  ]
[uunet!plains!grisanti          --         UUCP    ]
"Quantum Mechanics, the dreams that stuff is made of."
	-unknown

Re: Discrete FFT in basic

#296

Author: kwj
Date: Mon, 16 Nov 1992 16:40

28 lines
1353 bytes

An *excellent* book for numerical analyses is

        Press, W.H., Flannery, B.P., Teukolsky, S.A., and Vetterling,W.T.
        (1989).  Numerical Recipes:  The Art of Scientific Computing,
        Cambridge Unversity Press.

I use the FORTRAN version, which can easily be translated into BASIC.  I
believe that a BASIC version has been published, but I have not looked at
it yet.

Note:   Since the FFT is a convoluted (pun intended) algorithm, many 
        algorithms have errors in them, including the one in Numerical
        Recipes.  If you use the FORTRAN version, the algorithm has the
        line

                WPI = DSIN(THETA)

        This should be 

                WPI = -DSIN(THETA)

        This error will give you problems if you have a complex data set.

        I will post an algorithm that I wrote for a real (not complex) data
        set.  The algorithm is based on that by Press et al.

  kwj

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