alias demo

Plot one sampled waveform

% Try this:
% Set freq = 40 Hz (Nyquist frequency) and plot sine and then cosine

N = 81;
freq = 4;
t = linspace(0,1,81);
dt = t(2) - t(1);
fs = 1/dt;
fn = fs/2.0;
fprintf('sample frequency: %g Hz\n',fs);
str = sprintf('frequency %8.2f f_N\n',freq/fn);
x = 0.9*sin(2*pi*freq*t);
plot(t,x);
axis([0 1 -1 1]);
title(str);
xlabel('time (sec)');
ylabel('signal level');

sample frequency: 80 Hz

N = 81;
t = linspace(0,1,81);
dt = t(2) - t(1);
fs = 1/dt;
fn = fs/2;
close all;
aviobj = avifile('alias1.avi','Compression','Cinepak');
fig = figure;
for freq = [linspace(2,160,241) 4];
    x = 0.9*sin(2*pi*freq*t);
    plot(t,x);
    axis([0 1 -1 1]);
    xlabel('time (sec)');
    ylabel('signal level');
    str = sprintf('frequency %8.2f f_N\n',freq/fn);
    title(str);
    F = getframe(fig);
    aviobj = addframe(aviobj,F);
end
aviobj = close(aviobj);