--- /dev/null
+## Copyright (C) 1994 Dept of Probability Theory and Statistics TU Wien <Andreas.Weingessel@ci.tuwien.ac.at>
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## usage: cceps (x [, correct])
+##
+## Returns the complex cepstrum of the vector x.
+## If the optional argument correct has the value 1, a correction
+## method is applied. The default is not to do this.
+
+## Author: Andreas Weingessel <Andreas.Weingessel@ci.tuwien.ac.at>
+## Apr 1, 1994
+## Last modifified by AW on Nov 8, 1994
+
+function cep = cceps (x, c)
+
+ if (nargin == 1)
+ c = 0;
+ elseif (nargin != 2)
+ print_usage;
+ endif
+
+ [nr, nc] = size (x);
+ if (nc != 1)
+ if (nr == 1)
+ x = x';
+ nr = nc;
+ else
+ error ("cceps: x must be a vector");
+ endif
+ endif
+
+ bad_signal_message = ["cceps: bad signal x, ", ...
+ "some Fourier coefficients are zero."];
+
+ F = fft (x);
+ if (min (abs (F)) == 0)
+ error (bad_signal_message);
+ endif
+
+ # determine if correction necessary
+ half = fix (nr / 2);
+ cor = 0;
+ if (2 * half == nr)
+ cor = (c && (real (F (half + 1)) < 0));
+ if (cor)
+ F = fft (x(1:nr-1))
+ if (min (abs (F)) == 0)
+ error (bad_signal_message);
+ endif
+ endif
+ endif
+
+ cep = fftshift (ifft (log (F)));
+
+ # make result real
+ if (c)
+ cep = real (cep);
+ if (cor)
+ # make cepstrum of same length as input vector
+ cep (nr) = 0;
+ endif
+ endif
+
+endfunction