MATLAB Language Drawing Fast drawing
Example
There are three main ways to do sequential plot or animations: plot(x,y), set(h , 'XData' , y, 'YData' , y) and animatedline. If you want your animation to be smooth, you need efficient drawing, and the three methods are not equivalent.
% Plot a sin with increasing phase shift in 500 steps
x = linspace(0 , 2*pi , 100);
figure
tic
for thetha = linspace(0 , 10*pi , 500)
y = sin(x + thetha);
plot(x,y)
drawnow
end
toc
I get 5.278172 seconds.
The plot function basically deletes and recreates the line object each time. A more efficient way to update a plot is to use the XData and YData properties of the Line object.
tic
h = []; % Handle of line object
for thetha = linspace(0 , 10*pi , 500)
y = sin(x + thetha);
if isempty(h)
% If Line still does not exist, create it
h = plot(x,y);
else
% If Line exists, update it
set(h , 'YData' , y)
end
drawnow
end
toc
Now I get 2.741996 seconds, much better!
animatedline is a relatively new function, introduced in 2014b. Let's see how it fares:
tic
h = animatedline;
for thetha = linspace(0 , 10*pi , 500)
y = sin(x + thetha);
clearpoints(h)
addpoints(h , x , y)
drawnow
end
toc
3.360569 seconds, not as good as updating an existing plot, but still better than plot(x,y).
Of course, if you have to plot a single line, like in this example, the three methods are almost equivalent and give smooth animations. But if you have more complex plots, updating existing Line objects will make a difference.
