/usr/share/octave/packages/signal-1.3.2/freqs.m is in octave-signal 1.3.2-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 | ## Copyright (C) 2003 Julius O. Smith III <jos@ccrma.stanford.edu>
##
## 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/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{h} =} freqs (@var{b}, @var{a}, @var{w})
## @deftypefnx {Function File} {} freqs (@var{b}, @var{a}, @var{w})
##
## Compute the s-plane frequency response of the IIR filter B(s)/A(s) as
## H = polyval(B,j*W)./polyval(A,j*W). If called with no output
## argument, a plot of magnitude and phase are displayed.
##
## Example:
## @example
## b = [1 2]; a = [1 1];
## w = linspace (0, 4, 128);
## freqs (b, a, w);
## @end example
## @end deftypefn
function H = freqs(B,A,W)
if (nargin ~= 3 || nargout>1)
print_usage;
endif
H = polyval(B,j*W)./polyval(A,j*W);
if nargout<1
freqs_plot(W,H);
endif
endfunction
%!demo
%! B = [1 2];
%! A = [1 1];
%! w = linspace(0,4,128);
%! freqs(B,A,w);
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