Handle graphics and animation HELLLP!

The plot function plots a line and returns a handle to that line. This handle can be used to get or set the line’s properties after it has been created. Two of a line’s properties are XData and YData, which contain the x- and y-values currently plotted. Write a program that plots the function

x(t) = cos(2*pi*t – θ)

between the limits -1.0 ≤ t ≤ 1.0 and saves the handle of the resulting line. Remember, the smaller the increment, the smoother the plot. The angle θ is initially 0 radians.
Then, re-plot the line over and over with θ=p/10 rad, up to θ=2p rad. Again, the smaller the increment, the smoother the transition. To re-plot the lines, use a for loop to calculate new values for x and update the line’s XData property with the set command.

I have this so far

t = -1:0.1:1;
theta=0;

a = cos(2*pi*t-theta);

So I realize that during the for loop theta is going to increase by pi/10

theta=0;

n=0;

for theta<=2pi;

n=(n-1)+1

theta=n*(pi/10)

a = cos(2*pi*t-theta);

hndl=plot(t,a)

and thats all I have

[Walter Roberson]

n=(n-1)+1 is the same as n=n except if n is 0 and n is an unsigned integer (in which case n-1 is 0-1 which is clipped to 0 in unsigned calculations, and then the +1 would make it 1 instead of leaving n at 0.)

for theta<=2pi; is not valid syntax. "for" is used when you know how many times you are going to loop; to loop until a condition is satisfied use "while"

Answer 1

[Image Analyst]

Not too bad. Here, x is y (controlled by YData), and t ix x (controlled by XData). Try

% First do a plot to get hPlot.
for number_of_t_steps = 10 : 10 : 100
  t = linspace(-1, 1, number_of_t_steps)
  theta = 0; % or pi/10 or 2*pi
  xt = cos(2*pi*t - theta);
  set(hPlot, 'XDATA', t); % Adjust horizontal axis
  drawnow; % Force it to draw immediately.
  pause(1); % Wait a second for you to see it.
end

Realize that this only updates the horizontal axis, not the vertical.