polygonLength

POLYGONLENGTH Perimeter of a polygon.

   L = polygonLength(POLYGON);
   Computes the boundary length of a polygon. POLYGON is given by a N-by-2
   array of vertices. 

   Example
     % Perimeter of a circle approximation
     poly = circleToPolygon([0 0 1], 200);
     polygonLength(poly)
     ans =
         6.2829

   See also
   polygons2d, polygonCentroid, polygonArea, drawPolygon, polylineLength

0001 function len = polygonLength(poly, varargin)
0002 %POLYGONLENGTH Perimeter of a polygon.
0003 %
0004 %   L = polygonLength(POLYGON);
0005 %   Computes the boundary length of a polygon. POLYGON is given by a N-by-2
0006 %   array of vertices.
0007 %
0008 %   Example
0009 %     % Perimeter of a circle approximation
0010 %     poly = circleToPolygon([0 0 1], 200);
0011 %     polygonLength(poly)
0012 %     ans =
0013 %         6.2829
0014 %
0015 %   See also
0016 %   polygons2d, polygonCentroid, polygonArea, drawPolygon, polylineLength
0017 %
0018 
0019 % ------
0020 % Author: David Legland
0021 % E-mail: david.legland@inrae.fr
0022 % Created: 2005-05-11
0023 % Copyright 2005-2024 INRA - TPV URPOI - BIA IMASTE
0024 
0025 % If first argument is a cell array, this is a multi-polygon, and we simply
0026 % add the lengths of individual polygons
0027 if iscell(poly)
0028     len = 0;
0029     for i = 1:length(poly)
0030         len = len + polygonLength(poly{i});
0031     end
0032     return;
0033 end
0034 
0035 % case of a polygon given as two coordinate arrays
0036 if nargin == 2
0037     poly = [poly varargin{1}];
0038 end
0039 
0040 % check there are enough points
0041 if size(poly, 1) < 2
0042     len = 0;
0043     return;
0044 end
0045 
0046 % compute length
0047 if size(poly, 2) == 2
0048     % polygon in dimension 2 (classical case)
0049     dp = diff(poly([1:end 1], :), 1, 1);
0050     len = sum(hypot(dp(:, 1), dp(:, 2)));
0051 else
0052     % polygon of larger dimension
0053     len = sum(sqrt(sum(diff(poly([2:end 1], :), 1, 1).^2, 2)));
0054 end