/usr/share/octave/packages/signal-1.3.2/sos2tf.m is in octave-signal 1.3.2-1+b1.
This file is owned by root:root, with mode 0o644.
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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 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 | ## 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{b}, @var{a}] =} sos2tf (@var{sos})
## @deftypefnx {Function File} {[@var{b}, @var{a}] =} sos2tf (@var{sos}, @var{g})
## Convert series second-order sections to direct form @math{H(z) = B(z)/A(z)}.
##
## INPUTS:
## @itemize
##
## @item
## @var{sos} = matrix of series second-order sections, one per row:
## @example
## @var{sos} = [@var{B1}.' @var{A1}.'; ...; @var{BN}.' @var{AN}.']
## @end example
## where
## @code{@var{B1}.' = [b0 b1 b2] and @var{A1}.' = [1 a1 a2]} for
## section 1, etc. The b0 entry must be nonzero for each section.
## See @code{filter} for documentation of the second-order direct-form filter
## coefficients @var{B}i and @var{A}i.
##
## @item
## @var{g} is an overall gain factor that effectively scales
## the output @var{b} vector (or any one of the input @var{B}i vectors).
## If not given the gain is assumed to be 1.
## @end itemize
##
## RETURNED:
## @var{b} and @var{a} are vectors specifying the digital filter @math{H(z) = B(z)/A(z)}.
## See @code{filter} for further details.
##
## @seealso{tf2sos, zp2sos, sos2pz, zp2tf, tf2zp}
## @end deftypefn
function [B,A] = sos2tf(sos, g = 1)
if (nargin < 1 || nargin > 2)
print_usage;
endif
[N,M] = size(sos);
if M~=6
error('sos2tf: sos matrix should be N by 6');
endif
A = 1;
B = 1;
for i=1:N
B = conv(B, sos(i,1:3));
A = conv(A, sos(i,4:6));
endfor
nB = length(B);
while nB && B(nB)==0
B=B(1:nB-1);
nB=length(B);
endwhile
nA = length(A);
while nA && A(nA)==0
A=A(1:nA-1);
nA=length(A);
endwhile
B = B * g;
endfunction
%!test
%! B=[1 1];
%! A=[1 0.5];
%! [sos,g] = tf2sos(B,A);
%! [Bh,Ah] = sos2tf(sos,g);
%! assert({Bh,Ah},{B,A},10*eps);
%!test
%! B=[1 0 0 0 0 1];
%! A=[1 0 0 0 0 0.9];
%! [sos,g] = tf2sos(B,A);
%! [Bh,Ah] = sos2tf(sos,g);
%! assert({Bh,Ah},{B,A},100*eps);
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