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Phasor demo
% Phasor demo
%
% Tobin Fricke <tobin.fricke@ligo.org> 2011-06-08
% modulation depth
m = pi/4;
% vector of (normalized) frequencies to include
freqs = [0 1 -1 2 -2 3 -3 4 -4];
% initial amplitudes of the phasors
amp = besselj(freqs, m);
set(0, 'defaultlinelinewidth', 5);
% Set up the axes
cla reset;
axis equal;
xlim([-1 1.5]);
ylim([-1 1]);
% Draw the unit circle
rectangle('Position', [-1 -1 2 2], 'Curvature', [1 1])
% make some lines
L = [];
L(1) = line([0], [0]);
L(2) = line([0], [0], 'color', 'red');
save_to_disk = 0;
% how many frames to render?
if save_to_disk,
n_frames = 200;
else
n_frames = inf;
end
% how much the 1-Omega should rotate in one frame of the animation?
if isinf(n_frames)
dphi = 0.1;
else
dphi = (2*pi)/(n_frames + 1);
end
frameno = 0;
while (frameno < n_frames),
frameno = frameno + 1;
% Add up the phasors cumulatively
seg = cumsum([0 amp]);
% Draw both the collection of phasors and the resultant
set(L(1), 'xdata', real(seg), 'ydata', imag(seg));
set(L(2), 'xdata', real(seg([1,end])), 'ydata', imag(seg([1,end])));
% Update the display
drawnow;
if (save_to_disk),
print('-dpng', '-r72', sprintf('pm%03d.png', frameno));
else
pause(0.05);
end
% Advance the phasors for the next frame
amp = amp .* exp(1i * dphi * freqs);
end
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