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...

createDirectedCircle(varargin)
```function circle = createDirectedCircle(varargin)
%CREATEDIRECTEDCIRCLE Create a directed circle
%
%   C = createDirectedCircle(P1, P2, P3);
%   Creates a circle going through the given points.
%   C is a 1*4 array of the form: [XC YC R INV].
%   The last parameter is set to 1 if the points are located in clockwise
%   order on the circle.
%
%   C = createDirectedCircle(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.
%
%   circles2d, createCircle
%
%   ---------
%   author : David Legland
%   INRA - TPV URPOI - BIA IMASTE
%   created the 12/01/2005.
%

if nargin == 2
% inputs are the center and a point on the circle
p1 = varargin{1};
p2 = varargin{2};
x0 = (p1(:,1) + p2(:,1))/2;
y0 = (p1(:,2) + p2(:,2))/2;
r = hypot((p2(:,1)-p1(:,1)), (p2(:,2)-p1(:,2)))/2;

% circle is direct by default
d = 0;

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);
center = intersectLines(line1, line2);
x0 = center(:, 1);
y0 = center(:, 2);