arrow2.m

realize analysis and design for computer-controlled system

function arrow2(point,theta,scale)

%  ARROW2(point,theta,scale)  draw an arrow pointing in the
%  direction theta
%  Scale is an optional argument that will scale the size of the arrows
%  It is assumed that the axis limits are already set

%       8/4/93    Jeffery Faneuff Modified 97-08-04 BW
%       Copyright (c) 1988-93 by the MathWorks, Inc.

if nargin==2
  xl = get(gca,'xlim');
  yl = get(gca,'ylim');
  xd = xl(2)-xl(1);        % this sets the scale for the arrow size
  yd = yl(2)-yl(1);        % thus enabling the arrow to appear in correct 
  scale = (xd + yd) / 2;   % proportion to the current axis
end

hold on
axis(axis)

xx = [point(1)-0.02*scale*cos(theta+pi/8),point(1),... 
point(1)-0.02*scale*cos(theta-pi/8)]';
yy = [point(2)-0.02*scale*sin(theta+pi/8),point(2),... 
point(2)-0.02*scale*sin(theta-pi/8)]';

plot(xx,yy,'k-','linew',0.9)

hold off