polygong

 g = polygong(pointlist) or g = polygong(xlist,ylist) by Pruefert
 polygong returns a decomposed geometry matrix for a polygon object
 arguments can be
 (i) a pointlist of the form [x1 y1 x2 y2 ...]
 (ii) the koordinates of y and y component [x1 x2 ...] [y1 y2 ...]
 Examples
 (i) g =  polygong([0 1 0],[0 0 1]) triagle
 (ii) g =  polygong([0 0 1 0 0 1]) the same as (i)
 g = polygong(cos(linspace(0,2*pi,80)),sin(linspace(0,2*pi,80)))
 approximation on a circle by a "octadecagon" ;-) it is NOT the same as
 circleg
 NOTE the points of the polygon should be aranged in  counter clockwise
 order

0001 function g = polygong(varargin)
0002 % g = polygong(pointlist) or g = polygong(xlist,ylist) by Pruefert
0003 % polygong returns a decomposed geometry matrix for a polygon object
0004 % arguments can be
0005 % (i) a pointlist of the form [x1 y1 x2 y2 ...]
0006 % (ii) the koordinates of y and y component [x1 x2 ...] [y1 y2 ...]
0007 % Examples
0008 % (i) g =  polygong([0 1 0],[0 0 1]) triagle
0009 % (ii) g =  polygong([0 0 1 0 0 1]) the same as (i)
0010 % g = polygong(cos(linspace(0,2*pi,80)),sin(linspace(0,2*pi,80)))
0011 % approximation on a circle by a "octadecagon" ;-) it is NOT the same as
0012 % circleg
0013 % NOTE the points of the polygon should be aranged in  counter clockwise
0014 % order
0015 switch length(varargin)
0016     case 1
0017         pointlist = varargin{1};
0018         if mod(length(pointlist),2) == 1,
0019             error('number of x and y coordinates must be the same')
0020         end
0021     case 2
0022         if ~(length(varargin{1})==length(varargin{2})),
0023             error('xlist and ylist must have the same length')
0024         end
0025         nop = length(varargin{1});
0026         pointlist(1:2:2*nop) = varargin{1};
0027         pointlist(2:2:2*nop) = varargin{2};
0028     otherwise
0029         error('wrong number of input arguments')
0030 end
0031 
0032 
0033 % remove endpoint if it is also starting point
0034 if norm(pointlist(1:2)-pointlist(end-1:end))<1e-5,
0035     pointlist=pointlist(1:end-2);
0036 end
0037 nop = length(pointlist)/2;
0038 nokoords = length(pointlist);
0039 xpoints = pointlist(1:2:nokoords);
0040 ypoints = pointlist(2:2:nokoords);
0041 g = 2*ones(1,nop);
0042 g = [g;xpoints;xpoints(2:end),xpoints(1)];
0043 g = [g;ypoints;ypoints(2:end),ypoints(1)];
0044 g = [g;ones(1,nop);zeros(1,nop)];