%% Copyright (c) 2011, INRA
%% 2008-2011, 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{alpha2} =} normalizeAngle (@var{alpha})
%% @deftypefnx {Function File} {@var{alpha2} =} normalizeAngle (@var{alpha}, @var{center})
%% Normalize an angle value within a 2*PI interval
%%
%%   ALPHA2 = normalizeAngle(ALPHA);
%%   ALPHA2 is the same as ALPHA modulo 2*PI and is positive.
%%
%%   ALPHA2 = normalizeAngle(ALPHA, CENTER);
%%   Specifies the center of the angle interval.
%%   If CENTER==0, the interval is [-pi ; +pi]
%%   If CENTER==PI, the interval is [0 ; 2*pi] (default).
%%
%%   Example:
%%   % normalization between 0 and 2*pi (default)
%%   normalizeAngle(5*pi)
%%   ans =
%%       3.1416
%%
%%   % normalization between -pi and +pi
%%   normalizeAngle(7*pi/2, 0)
%%   ans =
%%       -1.5708
%%
%%   References
%%   Follows the same convention as apache commons library, see:
%%   http://commons.apache.org/math/api-2.2/org/apache/commons/math/util/MathUtils.html%% 
%%
%% @seealso{vectorAngle, lineAngle}
%% @end deftypefn

function alpha = normalizeAngle(alpha, varargin)

  center = pi;
  if ~isempty(varargin)
      center = varargin{1};
  end

  alpha = mod(alpha-center+pi, 2*pi) + center-pi;

endfunction

%!assert (pi/2, normalizeAngle (pi/2), 1e-6);
%!assert (pi, normalizeAngle (pi), 1e-6);
%!assert (3*pi/2, normalizeAngle (3*pi/2), 1e-6);
%!assert (pi/2, normalizeAngle (pi/2, pi), 1e-6);
%!assert (pi, normalizeAngle (pi, pi), 1e-6);
%!assert (3*pi/2, normalizeAngle (3*pi/2, pi), 1e-6);

%!test
%! theta = linspace(0, 2*pi-.1, 100);
%! assert(theta, normalizeAngle (theta), 1e-6);

%!assert (0, normalizeAngle (0, 0), 1e-6);
%!assert (pi/2, normalizeAngle (pi/2, 0), 1e-6);
%!assert (-pi, normalizeAngle (-pi, 0), 1e-6);
%!assert (-pi/2, normalizeAngle (7*pi/2, 0), 1e-6);

%!test
%! theta = linspace(-pi+.1, pi-.1, 100);
%! assert(theta, normalizeAngle (theta, 0), 1e-6);


