Animation delete previous point

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)
    addpoints(curve,x(i),y(i));
    drawnow
end

Answer 1

[Adam Danz]

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)
    addpoints(curve,x(i),y(i));
    drawnow
end

[Morten Jørgensen]

thanks for the help!

is this also possible to do with a scatterplot, where i plot 6 different points ?

[Adam Danz]

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.

[Lorenzo]

any way to plot not only the "last" point but also the line up to the last point (Not the entire line, the sin function in this example) Thank you

[Adam Danz]

ph = plot(nan(size(x)), nan(size(y)), 'r*');  %plot initial point
set(gca,'Xlim',[0 6.5], 'Ylim',[-1 1])
for i=1:numel(y)
    ph.XData(i) = x(i);         %change x coordinate of the point
    ph.YData(i) = y(i);         %change y coordinate of the point
    drawnow
    pause(0.05)  %control speed, if desired
end

[Walter Roberson]

An alterative animatedline approach to the original question is

curve = animatedline('MaximumNumPoints', 1);
for i= 1:length(Ball)
    addpoints(curve,x(i),y(i));
    drawnow
end