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plotting power spectrum density

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Kashish
Kashish on 21 May 2024 at 8:00
Commented: Kashish on 21 May 2024 at 9:15
I have 2 .dat file with me one of amplitude and one of time and I want to do the powerspectrum analysis of the data. Can anyone please help me in creating a time vector for doing FFT

Accepted Answer

Hassaan
Hassaan on 21 May 2024 at 8:32
% Load the data from the .dat files
amplitude = load('amplitude.dat');
time = load('time.dat');
% Check if time data is provided, otherwise create time vector
if isempty(time)
Fs = 1000; % Sampling frequency in Hz
Ts = 1 / Fs; % Sampling interval in seconds
time = (0:length(amplitude)-1) * Ts; % Time vector
end
% Compute FFT
L = length(amplitude); % Length of the signal
Y = fft(amplitude); % Compute the FFT
P2 = abs(Y / L); % Two-sided spectrum
P1 = P2(1:L/2+1); % Single-sided spectrum
P1(2:end-1) = 2 * P1(2:end-1);
f = Fs * (0:(L/2)) / L; % Frequency vector
% Calculate Power Spectrum Density (PSD)
PSD = (1 / (Fs * L)) * (abs(Y(1:L/2+1)).^2);
PSD(2:end-1) = 2 * PSD(2:end-1);
% Plot the PSD
figure;
plot(f, 10 * log10(PSD));
title('Power Spectrum Density');
xlabel('Frequency (Hz)');
ylabel('Power/Frequency (dB/Hz)');
grid on;
Notes
  1. Sampling Frequency (Fs): Ensure that you know the correct sampling frequency of your data. If it is not 1000 Hz, replace Fs = 1000 with the correct value.
  2. Units: The PSD is plotted in decibels (dB/Hz). The conversion is done using 10 * log10(PSD).
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It's important to note that the advice and code are based on limited information and meant for educational purposes. Users should verify and adapt the code to their specific needs, ensuring compatibility and adherence to ethical standards.
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  5 Comments
Hassaan
Hassaan on 21 May 2024 at 8:59
% Load the amplitude data
fileinfo = dir('amp-A-016.dat');
num_samples = fileinfo.bytes / 2;
fid = fopen('amp-A-016.dat', 'r');
amplitude = fread(fid, num_samples, 'int16');
fclose(fid);
amplitude = amplitude * 0.0000374;
% Load the time data
fileinfo = dir('time.dat');
num_samples = fileinfo.bytes / 4; % int32 = 4 bytes
fid = fopen('time.dat', 'r');
time = fread(fid, num_samples, 'int32');
fclose(fid);
time = time / 20000; % Adjust according to your sample rate
% Compute the sampling frequency (Fs) from time data
Fs = 1 / mean(diff(time)); % Sampling frequency in Hz
% Compute FFT
L = length(amplitude); % Length of the signal
Y = fft(amplitude); % Compute the FFT
P2 = abs(Y / L); % Two-sided spectrum
P1 = P2(1:L/2+1); % Single-sided spectrum
P1(2:end-1) = 2 * P1(2:end-1);
f = Fs * (0:(L/2)) / L; % Frequency vector
% Calculate Power Spectrum Density (PSD)
PSD = (1 / (Fs * L)) * (abs(Y(1:L/2+1)).^2);
PSD(2:end-1) = 2 * PSD(2:end-1);
% Plot the PSD
figure;
plot(f, 10 * log10(PSD));
title('Power Spectrum Density');
xlabel('Frequency (Hz)');
ylabel('Power/Frequency (dB/Hz)');
grid on;
Kashish
Kashish on 21 May 2024 at 9:15
thank you the code is working what if I want to do multitaper powerspectrum density method

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