how-to-draw-circle-in-matlab.txt

在MATLAB并无直接指令可进行画圆

function h=ellipse(ra,rb,ang,x0,y0,C,Nb) 

% Ellipse adds ellipses to the current plot 

% 

% 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 

% 

% Check the number of input arguments 

switch nargin 

case 0 

   ra=1;rb=1;ang=0;x0=0;y0=0;C=[];Nb=300; 

case 1 

   rb=ra;ang=0;x0=0;y0=0;C=[];Nb=300; 

case 2 

   ang=0;x0=0;y0=0;C=[];Nb=300; 

case 3 

   x0=0;y0=0;C=[];Nb=300; 

case 4 

   y0=zeros(1,length(x0));C=[];Nb=300; 

case 5 

   C=[];Nb=300; 

case 6 

   Nb=300; 

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(x0)~=length(y0), 

   if length(y0)==1, 

      y0=ones(1,length(x0))*y0; 

   elseif length(x0)==1, 

      x0=ones(1,length(y0))*x0; 

   else 

      error('The lengths of x0 and y0 must be identical'); 

   end; 

end; if length(ra)~=length(rb), 

   if length(ra)==1, 

      ra=ones(1,length(rb))*ra; 

   elseif length(x0)==1, 

      rb=ones(1,length(ra))*rb; 

   else 

      error('The lengths of ra and rb must be identical'); 

   end; 

end;   % how many inscribed elllipses are plotted 

 if length(ra)~=length(x0) 

  maxk=length(ra)*length(x0); 

else 

  maxk=length(ra); 

end; 

    % drawing loop 

route=0; 

if length(x0)==1, route=1; end 

if length(ra)==1, route=2; end 

if length(x0)==length(ra), route=3; end 

if length(ang)>1 & length(ra)==1, 

   route=4;maxk=length(ang); 

end 

 for k=1:maxk 

  switch route 

  case 1 

    xpos=x0; 

    ypos=y0; 

    radm=ra(k); 

    radn=rb(k); 

    if length(ang)==1, an=ang; else an=ang(k); end; 

  case 2 

    xpos=x0(k); 

    ypos=y0(k); 

    radm=ra; 

    radn=rb; 

    if length(ang)==1, an=ang; else an=ang(k); end; 

  case 3 

    xpos=x0(k); 

    ypos=y0(k); 

    radm=ra(k); 

    radn=rb(k); 

    if length(ang)==1, an=ang; else an=ang(k); end; 

  case 4 

    xpos=x0; 

    ypos=y0; 

    radm=ra; 

    radn=rb; 

    an=ang(k); 

  otherwise 

    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); 

%  x=radm*cos(the)*co-si*radn*sin(the)+xpos; 

%  y=radm*cos(the)*si+co*radn*sin(the)+ypos; 

  h(k)=line(radm*cos(the)*co-si*radn*sin(the)+xpos,radm*cos(the)*si+co*radn*sin(the)+ypos); 

  set(h(k),'color',C(rem(k-1,size(C,1))+1,:)); 

 end; 

axis equal;grid on;