# Animation delete previous point

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Morten Jørgensen on 28 Feb 2019
Edited: Adam Danz on 12 Mar 2019
Hi
I'm trying to make an animation, where I only display one point at the time, right now the trajectory stays, and I want only one point displayed
any suggestions, i want it to look like this: https://www.youtube.com/watch?v=q1dqIcLi3N0
this is my code so far
x= Ball(:,1);
y= Ball(:,2);
%%
figure
curve = animatedline('marker','*','Color','r');
set(gca,'Xlim',[-6000 6000], 'Ylim',[-4000 4000])
for i= 1:length(Ball)
drawnow
end

Adam Danz on 28 Feb 2019
Edited: Adam Danz on 28 Feb 2019
If your task is that simple, I prefer updating the XData and YData rather than using the animatedline method. This is faster and more efficient. Instead of deleting and drawing a new point on each iteration, it merely changes the coordinate value of the point that is already drawn. If this is too fast, you can control the approximate timing by using pause() within the loop to slow it down.
Here's an example (just run this to watch a dot move along a sinusoidal trajectory).
x= 0:0.1:2*pi;
y= sin(x);
figure
ph = plot(x(1), y(1), 'r*'); %plot initial point
set(gca,'Xlim',[0 6.5], 'Ylim',[-1 1])
for i=1:length(y)
ph.XData = x(i); %change x coordinate of the point
ph.YData = y(i); %change y coordinate of the point
drawnow
pause(0.05) %control speed, if desired
end
If you prefer to use the animatedline method, just insert clearpoints() before you call addpoints().
for i= 1:length(Ball)
clearpoints(curve)
drawnow
end
##### 2 CommentsShowHide 1 older comment
Adam Danz on 28 Feb 2019
Edited: Adam Danz on 12 Mar 2019
Yes. You can use this method with any graphic object that has the XData and YData (and ZData) properties. You're just replacing the coordinates of an object with new coordinates.