%%
Fs = 1000;                    % Sampling frequency
T = 1/Fs;                     % Sample time
L = 10000;                     % Length of signal
t = (0:L-1)*T;                % Time vector
% Sum of a 50 Hz sinusoid and a 120 Hz sinusoid

x = 2.8*sin(2*pi*50*t) + sin(2*pi*120*t);
y = 1*x + 10*randn(size(t));     % Sinusoids plus noise

% plot(Fs*t(1:50),y(1:50))
% title('Signal Corrupted with Zero-Mean Random Noise')
% xlabel('time (milliseconds)')
% NFFT = 2^nextpow2(L); % Next power of 2 from length of y
NFFT = 2000
Y = fft(y,NFFT)/L;
% f = Fs/2*linspace(0,1,NFFT/2); % Versao antiga do help estava errada
% Pot = abs(Y(1:NFFT/2)).^2; % Versao antiga do help estava errada
f = Fs/2*linspace(0,1,NFFT/2+1);
Pot = abs(Y(1:NFFT/2+1)).^2;
% Plot single-sided amplitude spectrum.

figure
subplot(2,1,1)
% plot(f,2*abs(Y(1:NFFT/2))) % Versao antiga do help estava errada
plot(f,2*abs(Y(1:NFFT/2+1)))
ylabel('|Y(f)|')
title('Single-Sided Amplitude Spectrum of y(t)')

subplot(2,1,2)
semilogy( f, Pot )
xlabel('Frequency (Hz)')
ylabel('Pot(f)')
