Make a point move straight up and down

Hi,

I would like to know how to plot a point and just make it go up, down, and back to the starting point. I was thinking about making a list of y values but was not sure if there was a simpler way.

Thanks

Answer 1

[Sulaymon Eshkabilov]

Hi,

A simple motion or animation tool with plot tools is drawnow that can be employed in your task, e.g.:

https://www.mathworks.com/help/matlab/ref/drawnow.html?s_tid=srchtitle

[SS]

I tried it out and it does not seem to show the up and down motion. Is there something I am missing?

[SS]

x = 0:.01:50; %linspace of x

y = sin(x); %wave equation

px = 0; %initial x plot

py = 0; %initial y plot

for i=1:1000 %loop

set(gcf,'DoubleBuffer', 'on');

h = patch([0 1 0 1], [0 1 1 0], 'r');

hold on

figure(100); %so code will replot over the previous figure, and not make a new one.

hold off

py = y(i)

plot(x,y, px, py,'o'); %circle point

pause(0.02); %speed of moving point

end

Here is what I have. But when I overlay an image on it, it flickers. I also want to get rid of the sine wave, and just keep the point moving up and down.

Answer 2

[Sulaymon Eshkabilov]

Hi,

If I've understood your question correctly, you'd like to get a up and down motion of a point x, y(i). Then here is one of the possible animated plots with drawnow:

for ii=1:numel(x) %loop
    plot(x,y, '--', px, y(ii),'o', 'markerfacecolor', 'y'); %circle point 
    hold off
    drawnow
end

[SS]

Hi, thank you! that works. However, additionally, I wanted to show the dot moving on a picture that I uploaded, so I want to hide the sine wave and just show the dot. When I add the picture, the whole thing flickers. How would I hide both the wave and prevent the flickering? You can see the code I have in the above comment. I apologize for all the questions.