%% Animate Graphics Object
% This example shows how to animate a triangle looping around the inside of
% a circle by updating the data properties of the triangle.
%%
% Plot the circle and set the axis limits so that the data units are
% the same in both directions.

% Copyright 2015 The MathWorks, Inc.


theta = linspace(-pi,pi);
xc = cos(theta);
yc = -sin(theta);
plot(xc,yc);
axis equal

%%
% Use the |area| function to draw a flat triangle. Then, change the value
% of one of the triangle vertices using the (x,y) coordinates of the
% circle. Change the value in a loop to create an animation. Use a
% <docid:matlab_ref.f56-719157> or |drawnow limitrate| command to display
% the updates after each iteration. |drawnow limitrate| is fastest, but it
% might not draw every frame on the screen.

xt = [-1 0 1 -1];
yt = [0 0 0 0];
hold on
t = area(xt,yt); % initial flat triangle
hold off
for j = 1:length(theta)-10
    xt(2) = xc(j); % determine new vertex value
    yt(2) = yc(j); 
    t.XData = xt; % update data properties 
    t.YData = yt;
    drawnow limitrate % display updates
end

%%
% The animation shows the triangle looping around the inside of the circle.