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comparison FIXES/tf2zp.m @ 0:6b33357c7561 octave-forge

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Initial revision
author pkienzle
date Wed, 10 Oct 2001 19:54:49 +0000
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-1:000000000000 0:6b33357c7561
1 ## Copyright (C) 1999 Paul Kienzle
2 ##
3 ## This program is free software; you can redistribute it and/or modify
4 ## it under the terms of the GNU General Public License as published by
5 ## the Free Software Foundation; either version 2 of the License, or
6 ## (at your option) any later version.
7 ##
8 ## This program is distributed in the hope that it will be useful,
9 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 ## GNU General Public License for more details.
12 ##
13 ## You should have received a copy of the GNU General Public License
14 ## along with this program; if not, write to the Free Software
15 ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
16
17 ## usage: [z, p, g] = tf2zp(b,a)
18 ##
19 ## Convert transfer function f(x)=sum(b*x^n)/sum(a*x^n) to
20 ## zero-pole-gain form f(x)=g*prod(1-z*x)/prod(1-p*x)
21
22 ## TODO: See if tf2ss followed by ss2zp gives better results. These
23 ## TODO: are available from the control system toolbox. Note that
24 ## TODO: the control systems toolbox doesn't bother, but instead uses
25 ## TODO: roots(b) and roots(a) as we do here (though they are very
26 ## TODO: long-winded about it---must ask why).
27 function [z, p, g] = tf2zp(b, a)
28 if nargin!=2 || nargout!=3,
29 usage("[z, p, g] = tf2zp(b, a)");
30 endif
31 if isempty(b) || isempty(a)
32 error("tf2zp b or a is empty. Perhaps already in zero-pole form?");
33 endif
34 g = b(1)/a(1);
35 z = roots(b);
36 p = roots(a);
37 endfunction