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circle.m
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circle.m
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%CIRCLE Compute points on a circle
%
% CIRCLE(C, R, OPTIONS) plots a circle centred at C (1x2) with radius R on the current
% axes.
%
% X = CIRCLE(C, R, OPTIONS) is a matrix (2xN) whose columns define the
% coordinates [x,y] of points around the circumferance of a circle
% centred at C (1x2) and of radius R.
%
% C is normally 2x1 but if 3x1 then the circle is embedded in 3D, and X is Nx3,
% but the circle is always in the xy-plane with a z-coordinate of C(3).
%
% Options::
% 'n',N Specify the number of points (default 50)
% Copyright (C) 1993-2017, by Peter I. Corke
%
% This file is part of The Robotics Toolbox for MATLAB (RTB).
%
% RTB is free software: you can redistribute it and/or modify
% it under the terms of the GNU Lesser General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% RTB 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 Lesser General Public License for more details.
%
% You should have received a copy of the GNU Leser General Public License
% along with RTB. If not, see <http://www.gnu.org/licenses/>.
%
% http://www.petercorke.com
function out = circle(centre, rad, varargin)
opt.n = 50;
[opt,arglist] = tb_optparse(opt, varargin);
% compute points on circumference
th = [0:opt.n-1]'/ opt.n*2*pi;
x = rad*cos(th) + centre(1);
y = rad*sin(th) + centre(2);
% add extra row if z-coordinate is specified, but circle is always in xy plane
if length(centre) > 2
z = ones(size(x))*centre(3);
p = [x y z]';
else
p = [x y]';
end
if nargout > 0
% return now
out = p;
return;
else
% else plot the circle
p = [p p(:,1)]; % make it close
if numrows(p) > 2
plot3(p(1,:), p(2,:), p(3,:), arglist{:});
else
plot(p(1,:), p(2,:), arglist{:});
end
end