Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / tf2sos.m

diff --git a/octave_packages/signal-1.1.3/tf2sos.m b/octave_packages/signal-1.1.3/tf2sos.m
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+%% Copyright (C) 2005 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{sos}, @var{g}] =} tf2sos (@var{B}, @var{A})
+%% Convert direct-form filter coefficients to series second-order sections.
+%%
+%% INPUTS:
+%% @var{B} and @var{A} are vectors specifying the digital filter @math{H(z) = B(z)/A(z)}.
+%% See @code{filter()} for documentation of the @var{B} and @var{A} 
+%% filter coefficients.
+%%
+%% RETURNED:
+%% @var{sos} = matrix of series second-order sections, one per row:@*
+%% @var{sos} = [@var{B1}.' @var{A1}.'; ...; @var{BN}.' @var{AN}.'], where@*
+%% @code{@var{B1}.'==[b0 b1 b2] and @var{A1}.'==[1 a1 a2]} for 
+%% section 1, etc.@*
+%% b0 must be nonzero for each section (zeros at infinity not supported).
+%% @var{Bscale} is an overall gain factor that effectively scales
+%% any one of the @var{B}i vectors.
+%%
+%% EXAMPLE:
+%% @example
+%% B=[1 0 0 0 0 1]; 
+%% A=[1 0 0 0 0 .9];
+%% [sos,g] = tf2sos(B,A)
+%%
+%% sos =
+%%
+%%    1.00000   0.61803   1.00000   1.00000   0.60515   0.95873
+%%    1.00000  -1.61803   1.00000   1.00000  -1.58430   0.95873
+%%    1.00000   1.00000  -0.00000   1.00000   0.97915  -0.00000
+%%
+%% g = 1
+%%
+%% @end example
+%%
+%% @seealso{sos2tf zp2sos sos2pz zp2tf tf2zp}
+%% @end deftypefn
+
+function [sos,g] = tf2sos (B, A)
+
+  [z,p,g] = tf2zp(B(:)',A(:)');
+  sos = zp2sos(z,p,g);
+
+endfunction
+
+%!test
+%! B=[1 0 0 0 0 1]; A=[1 0 0 0 0 .9];
+%! [sos,g] = tf2sos(B,A);
+%! [Bh,Ah] = sos2tf(sos,g);
+%! assert({Bh,Ah},{B,A},100*eps);