%% Copyright (c) 2011, INRA
%% 2004-2011, 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{line} = } cartesianLine (@var{A}, @var{B},@var{C})
%% Create a straight line from cartesian equation coefficients.
%%
%%   Create a line verifying the Cartesian equation:
%%   @var{A}*x + @var{B}*x + @var{C} = 0;
%%
%%   @seealso{lines2d, createLine}
%% @end deftypefn

function line = cartesianLine(varargin)

  if length(varargin)==1
      var = varargin{1};
      a = var(:,1);
      b = var(:,2);
      c = var(:,3);
  elseif length(varargin)==3
      a = varargin{1};
      b = varargin{2};
      c = varargin{3};
  end

  % normalisation factor
  d = a.*a + b.*b;

  x0 = -a.*c./d;
  y0 = -b.*c./d;
  theta = atan2(-a, b);
  dx = cos(theta);
  dy = sin(theta);

  line = [x0 y0 dx dy];

endfunction