Sinusoid, envelope, freq sweep

clear;
warning off;

%
% A sinusoid base signal (optionally with a gaussian envelope) and a freq sweep in a dot product plot
%
% multiply base signal with gaussian bell or not
gaussian_envelope = false

% sample rate, time base
srate = 500;
time  = -1:1/srate:1-1/srate;

% base signal
freq = 5;
phase = 0*pi/4;
base = sin(2 * pi * freq * time + phase);
% multiplied by gaussian envelope
if gaussian_envelope
  envelope = exp((-time .** 2) / .1);
else
  envelope = ones(1, length(time)); % identity
end
signal = base .* envelope;

% plot base signal (and gaussian)
subplot(211);
hold on, grid on
plot(time, envelope, 'g', 'linew', 2);
plot(time, signal, 'k', 'linew', 3);
hold off;
title('Signal with envelope');
% not required because of autoscale later
% set(gca, 'xlim', [-1 1]);

% dot product with signal and frequency sweep
sweep_freqs = 2:.2:8; % 2Hz to 8Hz with step of .2Hz
dot_prods = zeros(length(sweep_freqs));
for sweep_freq_index = 1:length(sweep_freqs)
  sweep_signal = sin(2 * pi * sweep_freqs(sweep_freq_index) * time);
  dot_prods(sweep_freq_index) = dot(sweep_signal, signal); % / length(time);
endfor

% stem plot for dot prod / sweep frequencies
subplot(212);
hold on, grid on
stem(sweep_freqs, dot_prods, 'k', 'linew', 3, 'markersize', 10, 'markerfacecolor', 'b');
hold off
title('Dot products by sweep frequency');
% not required because of autoscale later
% set(gca, 'ylim', [sweep_freqs(1)-.5 sweep_freqs(end)+.5], 'ylim', [-2 2]);

% autoscale now
axis("auto");

% print('dot_prod_w_gaussian_envelope.svg', '-dsvg', '-S1280,1024');
waitforbuttonpress();