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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function circle = createCircle(varargin)
%CREATECIRCLE Create a circle from 2 or 3 points.
%
% C = createCircle(P1, P2, P3);
% Creates the circle passing through the 3 given points.
% C is a 1*3 array of the form: [XC YX R].
%
% C = createCircle(P1, P2);
% Creates the circle whith center P1 and passing throuh the point P2.
%
% Works also when input are point arrays the same size, in this case the
% result has as many lines as the point arrays.
%
% Example
% % Draw a circle passing through 3 points.
% p1 = [10 15];
% p2 = [15 20];
% p3 = [10 25];
% circle = createCircle(p1, p2, p3);
% figure; hold on; axis equal; axis([0 50 0 50]);
% drawPoint([p1 ; p2; p3]);
% drawCircle(circle);
%
% See also
% circles2d, createDirectedCircle
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2003-10-31
% Copyright 2003-2023 INRA - TPV URPOI - BIA IMASTE
if nargin == 2
% inputs are the center and a point on the circle
p1 = varargin{1};
p2 = varargin{2};
x0 = p1(:,1);
y0 = p1(:,2);
r = hypot((p2(:,1)-x0), (p2(:,2)-y0));
elseif nargin == 3
% inputs are three points on the circle
p1 = varargin{1};
p2 = varargin{2};
p3 = varargin{3};
% compute circle center
line1 = medianLine(p1, p2);
line2 = medianLine(p1, p3);
point = intersectLines(line1, line2);
x0 = point(:, 1);
y0 = point(:, 2);
% circle radius
r = hypot((p1(:,1)-x0), (p1(:,2)-y0));
end
% create array for returning result
circle = [x0 y0 r];
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