(User.programs)
Item: 274 by _fbaird at hpcvbbs.UUCP
Author: [Frank Gregory Baird]
  Subj: FFT plotting
  Date: Fri May 03 1991

This is an FFT program taken from Oppenheim and Schafer's Digital Signal
Processing. The first argument is a complex 2^n-element vector. The
second argument is 1 for a forward FFT, and -1 for a backward (inverse)
FFT. Also included is a neat little program PLFFT which plots the
magnitudes the results of the FFT program. If the plot doesn't look
right, you may need to execute a RESET first. If this doesn't fix all the
problems, you may wish to also execute 'X' INDEP first. Alternatively you
may add this code
 { (-6.5,-3.1) (6.5,3.2) X 0 (0,0) BAR Y } 'PPAR' STO
 # 83h # 40h PDIM
before
 1 XCOL BARPLOT GRAPH.
 
Example:
Enter the 16-element vector (16x1 matrix) then a 1 for a forward FFT
[ (1,0) (1,0) (1,0) (1,0)
  (0,0) (0,0) (0,0) (0,0)
  (0,0) (0,0) (0,0) (0,0)
  (0,0) (0,0) (0,0) (0,0) ]
1
The returned result is also a 16-element vector
[ (4,0) 
  (3.01366974607,-2.01366974607)
  (.999999999998,-2.41421356237)
  (-.248302881332,-1.24830288133)
  (0,0)
  (.834089318959,.165910681042)
  (1,-.41421356237)
  (.40054381631,-.599456183685)
  (0,0)
  (.40054381631,.599456183693)
  (1,.41421356237)
  (.834089318956,-.165910681041)
  (0,0)
  (-.248302881331,1.24830288133)
  (.999999999999,2.41421356237)
  (3.01366974607,2.01366974606) ]

Author:
Frank G. Baird
HP BBS: fbaird
Internet:UG0342@applelink.apple.com.