Xi-Language Reference: Fast Fourier Transform
- fft (Multivariate fast fourier transform)
- rev_fft (Multivariate fast fourier transform)
Parameters
fft ( array, index... )
Types: array complex[]
index... int
Return
complex[] (fast fourier transform, space to frequency)
Description
fft performs a multivariate complex fast fourier transform to
go form space to frequency using mixed-radix fast fourier transform
algorithm. The parameter array contains a multidimensional array
for which the FFT should be computed. The parameters index1, index2 etc.
determine the indices over which the FFT will be performed. If these
parameters are omitted the function fft computes the complete FFT of the
input array.
Example
( 1)>a=dincarr(3,3);
( 2)>b=fft(a);
( 3)>e=fft(a,0,1);
( 4)>c=fft(a,0);
( 5)>d=fft(c,1);
now b, d and e are equal
See also
rev_fft
Reference
This function is based on the subroutine multifft in the
GO collection.(By R.C. Singleton, Stanford Research
Institute, Sept. 1968).
Parameters
rev_fft ( array, index... )
Types: array complex[]
index... int
Return
complex[] (fast fourier transform, frequency to space)
Description
rev_fft performs a multivariate complex fast fourier transform to
go form frequency to space using mixed-radix fast fourier transform
algorithm. The parameter array contains a multidimensional array
for which the FFT should be computed. The parameters index1, index2 etc.
determine the indices over which the FFT will be performed. If these
parameters are omitted the function fft computes the complete
FFT of the input array.
Example
( 1)>a=dincarr(3,3);
( 2)>b=rev_fft(a);
( 3)>c=rev_fft(a,0);
( 4)>e=fft(a,0,1);
( 5)>d=rev_fft(fft(a,0),0);
now e is equal b and d is equal a
See also
fft
Reference
This function is based on the subroutine multifft
in the GO collection.
(By R.C. Singleton, Stanford Research Institute, Sept. 1968).
© 1995 by Bodo Junglas, Klaus Spanderen and Fabian Weis
- Last revised: Wed Jun 19 16:58:32 1996