%% Copyright (c) 2011, INRA
%% 2003-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
%%
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%% -*- texinfo -*-
%% @deftypefn {Function File} {@var{h} = } drawCircle (@var{x0}, @var{y0}, @var{r})
%% @deftypefnx {Function File} {@var{h} = } drawCircle (@var{circle})
%% @deftypefnx {Function File} {@var{h} = } drawCircle (@var{center}, @var{radius})
%% @deftypefnx {Function File} {@var{h} = } drawCircle (@dots{}, @var{nstep})
%% @deftypefnx {Function File} {@var{h} = } drawCircle (@dots{}, @var{name}, @var{value})
%% 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.
%%
%%
%%   H = drawCircle(...);
%%   return handles to each created curve.
%%
%%   @seealso{circles2d, drawCircleArc, drawEllipse}
%% @end deftypefn

function varargout = drawCircle(varargin)

  % process input parameters
  var = varargin{1};
  if size(var, 2) == 1
      x0 = varargin{1};
      y0 = varargin{2};
      r  = varargin{3};
      varargin(1:3) = [];
      
  elseif size(var, 2) == 2
      x0 = var(:,1);
      y0 = var(:,2);
      r  = varargin{2};
      varargin(1:2) = [];
      
  elseif size(var, 2) == 3
      x0 = var(:,1);
      y0 = var(:,2);
      r  = var(:,3);
      varargin(1) = [];
  else
      error('bad format for input in drawCircle');
  end

  % ensure each parameter is column vector
  x0 = x0(:);
  y0 = y0(:);
  r = r(:);

  % default number of discretization steps
  N = 72;

  % check if discretization step is specified
  if ~isempty(varargin)
      var = varargin{1};
      if length(var)==1 && isnumeric(var)
          N = round(var);
          varargin(1) = [];
      end
  end

  % parametrization variable for circle (use N+1 as first point counts twice)
  t = linspace(0, 2*pi, N+1);
  cot = cos(t);
  sit = sin(t);

  % empty array for graphic handles
  h = zeros(size(x0));

  % compute discretization of each circle
  for i = 1:length(x0)
      xt = x0(i) + r(i) * cot;
      yt = y0(i) + r(i) * sit;

      h(i) = plot(xt, yt, varargin{:});
  end

  if nargout > 0
      varargout = {h};
  end

endfunction

