/usr/share/octave/packages/control-3.0.0/sigma.m is in octave-control 3.0.0-5.
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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 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 | ## Copyright (C) 2009-2015 Lukas F. Reichlin
##
## This file is part of LTI Syncope.
##
## LTI Syncope 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.
##
## LTI Syncope 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 LTI Syncope. If not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {} sigma (@var{sys})
## @deftypefnx {Function File} {} sigma (@var{sys1}, @var{sys2}, @dots{}, @var{sysN})
## @deftypefnx {Function File} {} sigma (@var{sys1}, @var{sys2}, @dots{}, @var{sysN}, @var{w})
## @deftypefnx {Function File} {} sigma (@var{sys1}, @var{'style1'}, @dots{}, @var{sysN}, @var{'styleN'})
## @deftypefnx{Function File} {[@var{sv}, @var{w}] =} sigma (@var{sys})
## @deftypefnx{Function File} {[@var{sv}, @var{w}] =} sigma (@var{sys}, @var{w})
## Singular values of frequency response. If no output arguments are given,
## the singular value plot is printed on the screen.
##
## @strong{Inputs}
## @table @var
## @item sys
## @acronym{LTI} system. Multiple inputs and/or outputs (MIMO systems) make practical sense.
## @item w
## Optional vector of frequency values. If @var{w} is not specified,
## it is calculated by the zeros and poles of the system.
## Alternatively, the cell @code{@{wmin, wmax@}} specifies a frequency range,
## where @var{wmin} and @var{wmax} denote minimum and maximum frequencies
## in rad/s.
## @item 'style'
## Line style and color, e.g. 'r' for a solid red line or '-.k' for a dash-dotted
## black line. See @command{help plot} for details.
## @end table
##
## @strong{Outputs}
## @table @var
## @item sv
## Array of singular values. For a system with m inputs and p outputs, the array sv
## has @code{min (m, p)} rows and as many columns as frequency points @code{length (w)}.
## The singular values at the frequency @code{w(k)} are given by @code{sv(:,k)}.
## @item w
## Vector of frequency values used.
## @end table
##
## @seealso{bodemag, svd}
## @end deftypefn
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: May 2009
## Version: 1.0
function [sv_r, w_r] = sigma (varargin)
if (nargin == 0)
print_usage ();
endif
[H, w, sty, leg] = __frequency_response__ ("sigma", varargin, nargout);
sv = cellfun (@(H) cellfun (@svd, H, "uniformoutput", false), H, "uniformoutput", false);
sv = cellfun (@(sv) horzcat (sv{:}), sv, "uniformoutput", false);
if (! nargout) # plot the information
## convert to dB for plotting
sv_db = cellfun (@mag2db, sv, "uniformoutput", false);
len = numel (H);
colororder = get (gca, "colororder");
rc = rows (colororder);
def = arrayfun (@(k) {"-", "color", colororder(1+rem (k-1, rc), :)}, 1:len, "uniformoutput", false);
idx = cellfun (@isempty, sty);
sty(idx) = def(idx);
plot_args = horzcat (cellfun (@horzcat, w, sv_db, sty, "uniformoutput", false){:});
## adjust line colors in legend
idx = horzcat (1, cellfun (@rows, sv_db)(1:end-1));
idx = cumsum (idx);
## plot results
h = semilogx (plot_args{:});
axis ("tight")
ylim (__axis_margin__ (ylim))
grid ("on")
title ("Singular Values")
xlabel ("Frequency [rad/s]")
ylabel ("Singular Values [dB]")
legend (h(idx), leg)
else # return values
sv_r = sv{1};
w_r = reshape (w{1}, [], 1);
endif
endfunction
%!shared sv_exp, w_exp, sv_obs, w_obs
%! A = [1, 2; 3, 4];
%! B = [5, 6; 7, 8];
%! C = [4, 3; 2, 1];
%! D = [8, 7; 6, 5];
%! w = [2, 3, 4];
%! sv_exp = [7.9176, 8.6275, 9.4393;
%! 0.6985, 0.6086, 0.5195];
%! w_exp = [2; 3; 4];
%! [sv_obs, w_obs] = sigma (ss (A, B, C, D), w);
%!assert (sv_obs, sv_exp, 1e-4);
%!assert (w_obs, w_exp, 1e-4);
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