function h=ellipse(ra,rb,ang,x0,y0,C,Nb, ax, varargin)
% Ellipse adds ellipses to the current plot
%
% MODIFIED BY AR 7/9/18: NOW REQUIRES A FULL 8 INPUTS FOR EVERY FUNCTION
% CALL AND THE AXES HANDLE MUST BE SPECIFIED AS THE LAST INPUT. THE REST OF THE
% DOCUMENTATION DOES NOT REFLECT THIS CHANGE.
%
%
% ELLIPSE(ra,rb,ang,x0,y0) adds an ellipse with semimajor axis of ra,
% a semimajor axis of radius rb, a semimajor axis of ang, centered at
% the point x0,y0.
%
% The length of ra, rb, and ang should be the same.
% If ra is a vector of length L and x0,y0 scalars, L ellipses
% are added at point x0,y0.
% If ra is a scalar and x0,y0 vectors of length M, M ellipse are with the same
% radii are added at the points x0,y0.
% If ra, x0, y0 are vectors of the same length L=M, M ellipses are added.
% If ra is a vector of length L and x0, y0 are  vectors of length
% M~=L, L*M ellipses are added, at each point x0,y0, L ellipses of radius ra.
%
% ELLIPSE(ra,rb,ang,x0,y0,C)
% adds ellipses of color C. C may be a string ('r','b',...) or the RGB value.
% If no color is specified, it makes automatic use of the colors specified by
% the axes ColorOrder property. For several circles C may be a vector.
%
% ELLIPSE(ra,rb,ang,x0,y0,C,Nb), Nb specifies the number of points
% used to draw the ellipse. The default value is 300. Nb may be used
% for each ellipse individually.
%
% h=ELLIPSE(...) returns the handles to the ellipses.
%
% as a sample of how ellipse works, the following produces a red ellipse
% tipped up at a 45 deg axis from the x axis
% ellipse(1,2,pi/8,1,1,'r')
%
% note that if ra=rb, ELLIPSE plots a circle
%
%
% written by D.G. Long, Brigham Young University, based on the
% CIRCLES.m original
% written by Peter Blattner, Institute of Microtechnology, University of
% Neuchatel, Switzerland, blattner@imt.unine.ch


% Check the number of input arguments

if nargin<1,
    ra=[];
end;
if nargin<2,
    rb=[];
end;
if nargin<3,
    ang=[];
end;

%if nargin==1,
%  error('Not enough arguments');
%end;

if nargin<5,
    x0=[];
    y0=[];
end;

if nargin<6,
    C=[];
end

if nargin<7,
    Nb=[];
end

linewidth = 1.5;
if ~isempty(varargin)
    linewidth = varargin{1};
end
% set up the default values

if isempty(ra),ra=1;end;
if isempty(rb),rb=1;end;
if isempty(ang),ang=0;end;
if isempty(x0),x0=0;end;
if isempty(y0),y0=0;end;
if isempty(Nb),Nb=300;end;
if isempty(C),C=get(gca,'colororder');end;

% work on the variable sizes

x0=x0(:);
y0=y0(:);
ra=ra(:);
rb=rb(:);
ang=ang(:);
Nb=Nb(:);

if isstr(C),C=C(:);end;

if length(ra)~=length(rb),
    error('length(ra)~=length(rb)');
end;
if length(x0)~=length(y0),
    error('length(x0)~=length(y0)');
end;

% how many inscribed elllipses are plotted

if length(ra)~=length(x0)
    maxk=length(ra)*length(x0);
else
    maxk=length(ra);
end;

% drawing loop

for k=1:maxk
    
    if length(x0)==1
        xpos=x0;
        ypos=y0;
        radm=ra(k);
        radn=rb(k);
        if length(ang)==1
            an=ang;
        else
            an=ang(k);
        end;
    elseif length(ra)==1
        xpos=x0(k);
        ypos=y0(k);
        radm=ra;
        radn=rb;
        an=ang;
    elseif length(x0)==length(ra)
        xpos=x0(k);
        ypos=y0(k);
        radm=ra(k);
        radn=rb(k);
        an=ang(k)
    else
        rada=ra(fix((k-1)/size(x0,1))+1);
        radb=rb(fix((k-1)/size(x0,1))+1);
        an=ang(fix((k-1)/size(x0,1))+1);
        xpos=x0(rem(k-1,size(x0,1))+1);
        ypos=y0(rem(k-1,size(y0,1))+1);
    end;
    
    co=cos(an);
    si=sin(an);
    the=linspace(0,2*pi,Nb(rem(k-1,size(Nb,1))+1,:)+1);
    temp1 = radm*cos(the);
    temp2 = radn*sin(the);
    x=temp1*co - si*temp2 + xpos;
    y=temp1*si + co*temp2 + ypos;
    
    h(k)=line(ax,x,y);
    set(h(k),'color',C(rem(k-1,size(C,1))+1,:), 'LineWidth', linewidth);
    
end

