Move a dot across screen video

Question

I'm having trouble in figuring out how to move a plotted dot across the screen in a movie. So let's say I plot a point:

plot(-1.4,-1.4, '.k', 'MarkerSize', 20)

and initialize a video object

vidObj = VideoWriter('dot.avi');
vidObj.Quality = 100;
vidObj.FrameRate = 10;
open(vidObj);

then how do I make the dot move to the right of the screen?

Answer 1

To make the dot moving across the right you can write a loop which plots the dot; at each iteration the X coordiantes of the point are incremented.

Within the loop you also have to capture each frame ad add it to the video file.

% Define the initial point's coords
P=[-1.4,-1.4];
% First plot
plot(P(1),P(2), '.k', 'MarkerSize', 20)
% Initialize the video
vidObj = VideoWriter('dot.avi');
vidObj.Quality = 100;
vidObj.FrameRate = 10;
open(vidObj);
% set axis properties
set(gca,'nextplot','replacechildren');
% Set xlim (max vaalue to be set according to the desired final position of
% the point)
set(gca,'xlim',[P(1)*2 150]);
% Loop for the point movement: 100 step, each iteration the pont in moved
% to the right of 1x (where x is the unito of measure of the space)
for i = 1:100
   plot(P(1)+i,P(2), '.k', 'MarkerSize', 20)
% Capture the current frame   
   currFrame = getframe;
% Add the current frame to the video file  
   writeVideo(vidObj,currFrame);
end
% Close the video file (stop recording)
close(vidObj);

Hope this helps.