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enclosingCircle.m    91 lines (76 with data), 3.4 kB

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## Copyright (C) 2004-2011 David Legland <david.legland@grignon.inra.fr>
## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## 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.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{circle} = } enclosingCircle (@var{pts})
## Find the minimum circle enclosing a set of points.
##
## CIRCLE = enclosingCircle(POINTS);
## compute cirlce CIRCLE=[xc yc r] which enclose all points POINTS given
## as an [Nx2] array.
##
##
## Rewritten from a file from
## Yazan Ahed
## which was rewritten from a Java applet by Shripad Thite :
## @url{http://heyoka.cs.uiuc.edu/~thite/mincircle/}
##
## @seealso{circles2d, points2d, boxes2d}
## @end deftypefn
function circle = enclosingCircle(pts)
# works on convex hull : it is faster
pts = pts(convhull(pts(:,1), pts(:,2)), :);
circle = recurseCircle(size(pts, 1), pts, 1, zeros(3, 2));
endfunction
function circ = recurseCircle(n, p, m, b)
# n: number of points given
# m: an argument used by the function. Always use 1 for m.
# bnry: an argument (3x2 array) used by the function to set the points that
# determines the circle boundry. You have to be careful when choosing this
# array's values. I think the values should be somewhere outside your points
# boundary. For my case, for example, I know the (x,y) I have will be something
# in between (-5,-5) and (5,5), so I use bnry as:
# [-10 -10
# -10 -10
# -10 -10]
if m==4
circ = createCircle(b(1,:), b(2,:), b(3,:));
return;
end
circ = [Inf Inf 0];
if m == 2
circ = [b(1,1:2) 0];
elseif m == 3
c = (b(1,:) + b(2,:))/2;
circ = [c distancePoints(b(1,:), c)];
end
for i = 1:n
if distancePoints(p(i,:), circ(1:2)) > circ(3)
if sum(b(:,1)==p(i,1) & b(:,2)==p(i,2)) == 0
b(m,:) = p(i,:);
circ = recurseCircle(i, p, m+1, b);
end
end
end
endfunction