drawCircle

DRAWCIRCLE Draw a circle on the current axis.

   drawCircle(X0, Y0, R);
   Draw the circle with center (X0,Y0) and the radius R. If X0, Y0 and R
   are column vectors of the same length, draw each circle successively.

   drawCircle(CIRCLE);
   Concatenate all parameters in a Nx3 array, where N is the number of
   circles to draw.

   drawCircle(CENTER, RADIUS);
   Specify CENTER as Nx2 array, and radius as a Nx1 array.

   drawCircle(..., NSTEP);
   Specify the number of edges that will be used to draw the circle.
   Default value is 72, creating an approximation of one point for each 5
   degrees.

   drawCircle(..., NAME, VALUE);
   Specifies plotting options as pair of parameters name/value. See plot
   documentation for details.

   drawCircle(AX, ...)
   Specifies the handle of the axis to draw on.

   H = drawCircle(...);
   return handles to each created curve.

   Example
     figure;
     hold on;
     drawCircle([10 20 30]);
     drawCircle([15 15 40], 'color', 'r', 'linewidth', 2);
     axis equal;

   See also
   circles2d, drawCircleArc, drawEllipse, circleToPolygon

0001 function varargout = drawCircle(varargin)
0002 %DRAWCIRCLE Draw a circle on the current axis.
0003 %
0004 %   drawCircle(X0, Y0, R);
0005 %   Draw the circle with center (X0,Y0) and the radius R. If X0, Y0 and R
0006 %   are column vectors of the same length, draw each circle successively.
0007 %
0008 %   drawCircle(CIRCLE);
0009 %   Concatenate all parameters in a Nx3 array, where N is the number of
0010 %   circles to draw.
0011 %
0012 %   drawCircle(CENTER, RADIUS);
0013 %   Specify CENTER as Nx2 array, and radius as a Nx1 array.
0014 %
0015 %   drawCircle(..., NSTEP);
0016 %   Specify the number of edges that will be used to draw the circle.
0017 %   Default value is 72, creating an approximation of one point for each 5
0018 %   degrees.
0019 %
0020 %   drawCircle(..., NAME, VALUE);
0021 %   Specifies plotting options as pair of parameters name/value. See plot
0022 %   documentation for details.
0023 %
0024 %   drawCircle(AX, ...)
0025 %   Specifies the handle of the axis to draw on.
0026 %
0027 %   H = drawCircle(...);
0028 %   return handles to each created curve.
0029 %
0030 %   Example
0031 %     figure;
0032 %     hold on;
0033 %     drawCircle([10 20 30]);
0034 %     drawCircle([15 15 40], 'color', 'r', 'linewidth', 2);
0035 %     axis equal;
0036 %
0037 %   See also
0038 %   circles2d, drawCircleArc, drawEllipse, circleToPolygon
0039 %
0040 
0041 % ------
0042 % Author: David Legland
0043 % E-mail: david.legland@inrae.fr
0044 % Created: 2003-10-31
0045 % Copyright 2003-2024 INRA - TPV URPOI - BIA IMASTE
0046 
0047 %% Parse input arguments
0048 
0049 % extract handle of axis to draw on
0050 [ax, varargin] = parseAxisHandle(varargin{:});
0051 
0052 % process input parameters
0053 var = varargin{1};
0054 if size(var, 2) == 1
0055     x0 = varargin{1};
0056     y0 = varargin{2};
0057     r  = varargin{3};
0058     varargin(1:3) = [];
0059     
0060 elseif size(var, 2) == 2
0061     x0 = var(:,1);
0062     y0 = var(:,2);
0063     r  = varargin{2};
0064     varargin(1:2) = [];
0065     
0066 elseif size(var, 2) == 3
0067     x0 = var(:,1);
0068     y0 = var(:,2);
0069     r  = var(:,3);
0070     varargin(1) = [];
0071 else
0072     error('bad format for input in drawCircle');
0073 end
0074 
0075 % default number of discretization steps
0076 N = 72;
0077 
0078 % check if discretization step is specified
0079 if ~isempty(varargin)
0080     var = varargin{1};
0081     if isnumeric(var) && isscalar(var)
0082         N = round(var);
0083         varargin(1) = [];
0084     end
0085 end
0086 
0087 
0088 %% Pre-processing
0089 
0090 % ensure each parameter is column vector
0091 x0 = x0(:);
0092 y0 = y0(:);
0093 r = r(:);
0094 
0095 % parametrization variable for circle (use N+1 as first point counts twice)
0096 t = linspace(0, 2*pi, N+1);
0097 cot = cos(t);
0098 sit = sin(t);
0099 
0100 % empty array for graphic handles
0101 h = zeros(size(x0));
0102 
0103 % save hold state
0104 holdState = ishold(ax);
0105 hold(ax, 'on');
0106 
0107 
0108 %% Display each circle
0109 
0110 % compute discretization of each circle
0111 for i = 1:length(x0)
0112     xt = x0(i) + r(i) * cot;
0113     yt = y0(i) + r(i) * sit;
0114 
0115     h(i) = plot(ax, xt, yt, varargin{:});
0116 end
0117 
0118 
0119 %% Post-processing
0120 
0121 % restore hold state
0122 if ~holdState
0123     hold(ax, 'off');
0124 end
0125 
0126 if nargout > 0
0127     varargout = {h};
0128 end