/usr/share/octave/packages/control-3.0.0/nichols.m is in octave-control 3.0.0-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | ## 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} {} nichols (@var{sys})
## @deftypefnx {Function File} {} nichols (@var{sys1}, @var{sys2}, @dots{}, @var{sysN})
## @deftypefnx {Function File} {} nichols (@var{sys1}, @var{sys2}, @dots{}, @var{sysN}, @var{w})
## @deftypefnx {Function File} {} nichols (@var{sys1}, @var{'style1'}, @dots{}, @var{sysN}, @var{'styleN'})
## @deftypefnx {Function File} {[@var{mag}, @var{pha}, @var{w}] =} nichols (@var{sys})
## @deftypefnx {Function File} {[@var{mag}, @var{pha}, @var{w}] =} nichols (@var{sys}, @var{w})
## Nichols chart of frequency response. If no output arguments are given,
## the response is printed on the screen.
##
## @strong{Inputs}
## @table @var
## @item sys
## @acronym{LTI} system. Must be a single-input and single-output (SISO) system.
## @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 mag
## Vector of magnitude. Has length of frequency vector @var{w}.
## @item pha
## Vector of phase. Has length of frequency vector @var{w}.
## @item w
## Vector of frequency values used.
## @end table
##
## @seealso{bode, nyquist, sigma}
## @end deftypefn
## Author: Lukas Reichlin <lukas.reichlin@gmail.com>
## Created: November 2009
## Version: 1.0
function [mag_r, pha_r, w_r] = nichols (varargin)
if (nargin == 0)
print_usage ();
endif
[H, w, sty, leg] = __frequency_response__ ("nichols", varargin, nargout);
H = cellfun (@reshape, H, {[]}, {1}, "uniformoutput", false);
mag = cellfun (@abs, H, "uniformoutput", false);
pha = cellfun (@(H) unwrap (arg (H)) * 180 / pi, H, "uniformoutput", false);
if (! nargout)
mag_db = cellfun (@mag2db, mag, "uniformoutput", false);
plot_args = horzcat (cellfun (@horzcat, pha, mag_db, sty, "uniformoutput", false){:});
plot (plot_args{:})
axis ("tight")
xlim (__axis_margin__ (xlim))
ylim (__axis_margin__ (ylim))
grid ("on")
title ("Nichols Chart")
xlabel ("Phase [deg]")
ylabel ("Magnitude [dB]")
legend (leg)
else
mag_r = mag{1};
pha_r = pha{1};
w_r = w{1};
endif
endfunction
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