Simple, but stumped. Using 'xline' to create animated "play marker" across waveform plot.

I am trying to create a plot of a waveform that has a "play marker"/vertical line running across. Have been trying with 'xline' drawing at position 'ii' in a for loop, but I can't figure out how to clear previous lines, so every line position stays on the plot. (Have included test data lines at the top so it can run.)

I know the solution is bound to be really simple, but it eludes me. Currently investigating whether the 'animatedline' function call is better suited.

Many thanks for any help.

Cheers.

Fs = 48000;
Position01 = rand(Fs,11);
StartIndex = 1;
FinishIndex = 100;

figure;
subplot(2,1,1);
plot(Position01(StartIndex:FinishIndex,11));
hold on
title('test');
xlabel('test');
ylabel('test');
subplot(2,1,2);
plot(Position01(StartIndex:FinishIndex,1));
title('test');
xlabel('test');
ylabel('test');
for ii = 1 : length(Position01(StartIndex:FinishIndex,11))
    
    xline(ii);
    drawnow
    
end

Answer 1

[Alan Moses]

You may use the following lines of code to clear the previous line:

children = get(gca, 'children');
delete(children(1));

The explanation to the above lines of code can be found here.

The above lines of code can be added to your script as follows:

for ii = 1 : length(Position01(StartIndex:FinishIndex,11))
    
    %Ensures the original plot stays and clears only the vertical lines plotted
    if(ii >= 2)
        children = get(gca, 'children');
        delete(children(1));
    end
    xline(ii);
    drawnow
    
end

Hope this helps!

[Peter Beringer]

Brilliant! Sorted it wonderfully. Thank you very much :)

Answer 2

[Steven Lord]

Rather than deleting and recreating the line, change its properties.

% Define the data
x = 0:360;
y = sind(x);

% Create three plots
plot(x, y); % Main sine curve
hold on
h = xline(x(1)); % vertical cursor
m = plot(x(1), y(1), 'ro'); % intersection circle

% Update the h and m lines
for whichX = 1:10:numel(x)
    h.Value = x(whichX);

    m.XData = x(whichX);
    m.YData = y(whichX);
    pause(0.25)
end

[Peter Beringer]

Wow, thanks. I actually find that a more elegant and efficient solution. And the intersection marker circle is a useful touch for my purposes. Thanks a lot!

(Is it possible to accept more than one answer?)