drawPolygon

DRAWPOLYGON Draw a polygon specified by a list of points.

   drawPolygon(POLY);
   Packs coordinates in a single N-by-2 array, with N the vertex number.

   drawPolygon(PX, PY);
   Specifies coordinates in separate arrays. Both array must be N-by-1,
   with N the number of vertices.

   drawPolygon(POLYS)
   Packs coordinate of several polygons in a cell array. Each element of
   the array is a Ni-by-2 double array.

   drawPolygon(..., NAME, VALUE);
   Specifies drawing options by using one or several parameter name-value
   pairs, see the doc of plot function for details.

   drawPolygon(AX, ...)
   Specifies the axis to draw the polygon on.

   H = drawPolygon(...);
   Also return a handle to the list of line objects.

   Example
     % draw a red rectangle
     poly = [10 10;40 10;40 30;10 30];
     figure; drawPolygon(poly, 'r');
     axis equal; axis([0 50 0 50]); 

     % Draw two squares
     px = [10 20 20 10 NaN 30 40 40 30]';
     py = [10 10 20 20 NaN 10 10 20 20]';
     figure; 
     drawPolygon([px py], 'lineWidth', 2);
     axis equal; axis([0 50 0 50]); 
 
   See also
   polygons2d, drawPolyline

0001 function varargout = drawPolygon (px, varargin)
0002 %DRAWPOLYGON Draw a polygon specified by a list of points.
0003 %
0004 %   drawPolygon(POLY);
0005 %   Packs coordinates in a single N-by-2 array, with N the vertex number.
0006 %
0007 %   drawPolygon(PX, PY);
0008 %   Specifies coordinates in separate arrays. Both array must be N-by-1,
0009 %   with N the number of vertices.
0010 %
0011 %   drawPolygon(POLYS)
0012 %   Packs coordinate of several polygons in a cell array. Each element of
0013 %   the array is a Ni-by-2 double array.
0014 %
0015 %   drawPolygon(..., NAME, VALUE);
0016 %   Specifies drawing options by using one or several parameter name-value
0017 %   pairs, see the doc of plot function for details.
0018 %
0019 %   drawPolygon(AX, ...)
0020 %   Specifies the axis to draw the polygon on.
0021 %
0022 %   H = drawPolygon(...);
0023 %   Also return a handle to the list of line objects.
0024 %
0025 %   Example
0026 %     % draw a red rectangle
0027 %     poly = [10 10;40 10;40 30;10 30];
0028 %     figure; drawPolygon(poly, 'r');
0029 %     axis equal; axis([0 50 0 50]);
0030 %
0031 %     % Draw two squares
0032 %     px = [10 20 20 10 NaN 30 40 40 30]';
0033 %     py = [10 10 20 20 NaN 10 10 20 20]';
0034 %     figure;
0035 %     drawPolygon([px py], 'lineWidth', 2);
0036 %     axis equal; axis([0 50 0 50]);
0037 %
0038 %   See also
0039 %   polygons2d, drawPolyline
0040 
0041 % ------
0042 % Author: David Legland
0043 % E-mail: david.legland@inrae.fr
0044 % Created: 2004-05-05
0045 % Copyright 2004-2024 INRA - TPV URPOI - BIA IMASTE
0046 
0047 % Store hold state
0048 state = ishold(gca);
0049 hold on;
0050 
0051 
0052 %% Check input
0053 if nargin < 1
0054     error ('should specify at least one argument');
0055 end
0056 
0057 % check for empty polygons
0058 if isempty (px)
0059     return
0060 end
0061 
0062 % extract handle of axis to draw on
0063 ax = gca;
0064 if isAxisHandle(px)
0065     ax          = px;
0066     px          = varargin{1};
0067     varargin(1) = [];
0068 end
0069 
0070 
0071 %% Manage cell arrays of polygons
0072 
0073 % case of a set of polygons stored in a cell array
0074 if iscell(px)
0075     h   = cellfun(@(x) drawPolygon(ax, x, varargin{:}), px, 'UniformOutput', 0);
0076     h   = horzcat(h{:});
0077     
0078 else
0079     % Check size vs number of arguments
0080     if size(px, 2) == 2
0081         % Case of polygon specified as a N-by-2 array (most standard case)
0082         py = px(:, 2);
0083         px = px(:, 1);
0084         
0085     elseif size(px, 2) == 1
0086         % Case of polygon specified as two N-by-1 arrays with same length
0087         if nargin < 2 || nargin == 2 && ~isnumeric(varargin{1})
0088             error('Matgeom:invalid_input_arg', ...
0089                 'Should specify either a N-by-2 array, or 2 N-by-1 vectors');
0090         end
0091         
0092         % Extract coordinates of polygon vertices
0093         py          = varargin{1};
0094         varargin(1) = [];
0095         
0096         if length(py) ~= length(px)
0097             error('Matgeom:invalid_input_arg', ...
0098                 'X and Y coordinate arrays should have same lengths (%d,%d)', ...
0099                 length(px), length(py)) 
0100         end
0101         
0102     else
0103         error('Matgeom:invalid_input_arg', 'Should specify a N-by-2 array');
0104     end
0105     
0106     % set default line format
0107     if isempty (varargin)
0108         varargin = {'b-'};
0109     end
0110    
0111     % Check case of polygons with holes
0112     if any (isnan (px(:)) )
0113         polygons = splitPolygons ([px py]);
0114         h        = drawPolygon (ax, polygons, varargin{:});
0115         
0116     else
0117         % ensure last point is the same as the first one
0118         px(end+1, :) = px(1,:);
0119         py(end+1, :) = py(1,:);
0120 
0121         % draw the polygon outline
0122         h = plot(ax, px, py, varargin{:});
0123         
0124     end % whether there where holes
0125     
0126 end % whether input arg was a cell
0127 
0128 if ~state
0129     hold off
0130 end
0131 
0132 % avoid returning argument if not required
0133 if nargout > 0
0134     varargout = {h};
0135 end