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plot_homline.m
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plot_homline.m
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%PLOT_HOMLINE Draw a line in homogeneous form
%
% PLOT_HOMLINE(L) draws a 2D line in the current plot defined in homogenous
% form ax + by + c = 0 where L (3x1) is L = [a b c].
% The current axis limits are used to determine the endpoints of
% the line. If L (3xN) then N lines are drawn, one per column.
%
% PLOT_HOMLINE(L, LS) as above but the MATLAB line specification LS is given.
%
% H = PLOT_HOMLINE(...) as above but returns a vector of graphics handles for the lines.
%
% Notes::
% - The line(s) is added to the current plot.
% - The line(s) can be drawn in 3D axes but will always lie in the
% xy-plane.
%
% Example::
% L = homline([1 2]', [3 1]'); % homog line from (1,2) to (3,1)
% plot_homline(L, 'k--'); % plot dashed black line
%
% See also PLOT_BOX, PLOT_POLY, HOMLINE.
% Copyright (C) 1993-2019 Peter I. Corke
%
% This file is part of The Spatial Math Toolbox for MATLAB (SMTB).
%
% Permission is hereby granted, free of charge, to any person obtaining a copy
% of this software and associated documentation files (the "Software"), to deal
% in the Software without restriction, including without limitation the rights
% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
% of the Software, and to permit persons to whom the Software is furnished to do
% so, subject to the following conditions:
%
% The above copyright notice and this permission notice shall be included in all
% copies or substantial portions of the Software.
%
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
% FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
% COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
% IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
% CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
%
% https://github.com/petercorke/spatial-math
function handles = plot_homline(lines, varargin)
% get plot limits from current graph
xlim = get(gca, 'XLim');
ylim = get(gca, 'YLim');
ish = ishold;
hold on;
if min(size(lines)) == 1
lines = lines(:);
end
assert(numrows(lines) == 3, 'SMTB:plot_homline:badarg', 'Input must be a 3-vector or 3xN matrix');
h = [];
% for all input lines (columns
for l=lines
if abs(l(2)) > abs(l(1))
y = (-l(3) - l(1)*xlim) / l(2);
hh = plot(xlim, y, varargin{:});
else
x = (-l(3) - l(2)*ylim) / l(1);
hh = plot(x, ylim, varargin{:});
end
h = [h; hh];
end
if ~ish
hold off
end
if nargout > 0,
handles = h;
end