Code covered by the BSD License

# geom2d

### David Legland (view profile)

13 Jun 2005 (Updated )

Geometry library for matlab. Performs geometric computations on points, lines, circles, polygons...

createCircle(varargin)
```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);
%
%   circles2d, createDirectedCircle
%
%   ---------
%   author : David Legland
%   INRA - TPV URPOI - BIA IMASTE
%   created the 31/10/2003.
%

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);