Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / freqs.m

diff --git a/octave_packages/signal-1.1.3/freqs.m b/octave_packages/signal-1.1.3/freqs.m
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+## 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/>.
+
+## Usage: H = freqs(B,A,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:
+##    B = [1 2]; A = [1 1];
+##    w = linspace(0,4,128);
+##    freqs(B,A,w);
+
+function [H] = freqs(B,A,W)
+
+  if (nargin ~= 3 || nargout>1)
+    print_usage;
+  end
+
+  H = polyval(B,j*W)./polyval(A,j*W);
+
+  if nargout<1
+    freqs_plot(W,H);
+  end
+
+endfunction
+
+%!demo
+%! B = [1 2];
+%! A = [1 1];
+%! w = linspace(0,4,128);
+%! freqs(B,A,w);