Clearing the last plotted image in a for loop.

I want this program (see below), to plot a blue circle travelling in a circular path. The radius of the path is the variable r and the orbital period is the variable T. The problem I'm having is that the previous blue circles aren't deleted. The plot looks like this:

function solsystem(r,T)

bildNr = 0;

for t=linspace(0,10,100)

plot(r.*cos(2/pi-w*t),r.*sin(2/pi-w*t),'bo')

drawPath(r)

plot(0,0,'o','MarkerSize',10,'MarkerEdgeColor','k','MarkerFaceColor','y')

var(r,T)

figure(1),clf;

bildNr = bildNr +1;

film(bildNr)=getframe;

end

function drawPath(r)

beta = linspace(0, 2*pi);

plot(r.*cos(beta),r.*sin(beta),'k');

axis equal;

end

function var(T)

w = 2*pi./T; %vinkelhastighet%

end

end

Answer 1

[MarKf]

The function provided does not work out of the box (and you haven't boxed it in code format anyway) so you have more than the issue of not having the previous dot disappear.

If that were the only issue you could just capture the object when you plot with a handle and then delete only that afterwards before plotting the next, no need to clear with clf and recreate the figure ( ho = plot(...,'bo'); delete(ho) ).

See below.

%% function solsystem(r,T)
r = 10; T = 5; center = [0,0];
bildNr = 0; w = wvar(T);
plot(center(1),center(2),'o','MarkerSize',10,'MarkerEdgeColor','k','MarkerFaceColor','y')
axis([center(1)-r,center(1)+r,center(2)-r,center(2)+r].*1.1), axis equal, 
hold on
hp = drawPath(r); %should this just draw just the travelled circular path 
% (then put back inside loop and get sector)? if it's the whole thing can stay out like yellow center
for t=linspace(0,10,4) %4 just to show
    if t, delete(ho), end
    ho = plot(r.*cos(2/pi-w*t),r.*sin(2/pi-w*t),'bo');
    bildNr = bildNr +1;
    film(bildNr)=getframe; %could preallocate
    filmdat(:,:,:,bildNr) = film(bildNr).cdata;
end

figure
montage(filmdat) %immovie/implay or the moving above does not work in online answers

function h = drawPath(r)
        beta = linspace(0, 2*pi);
        h = plot(r.*cos(beta),r.*sin(beta),'k');
end
function w = wvar(T)
        w = 2*pi./T; %vinkelhastighet%
end
    
% end 

[Jakob]

Thank you! Naming the plot and using the delete() function worked wonders!