Problems with mathlab FFS

Discussion in 'Programmer's Corner' started by REPresent, Jul 12, 2013.

  1. REPresent

    Thread Starter New Member

    Jul 12, 2013
    1
    0
    Hello,
    Im making research on humans gait and I found some troubles with matlab. I need given data in file pass through Fast fourier transformation. In given file taken column as X axe are samples of acceleration (which varies depending on movement). Frequence of device is 120Hz. In figure1 X axe is Time(s), Y axe is Acceleration(m/s^2) The main matter is how to make Spectrum of this Acceleration wave that in X axe would be Frequence and in Y axe would be Acceleration.

    I inlcuded data text file named MTbeapsisukimo2:
    http://www.megafileupload.com/en/file/434206/MTbeapsisukimo2-txt.html
    Theres the code where I was trying to make X axe - as a frequence and Y axe as a Power:

    Code ( (Unknown Language)):
    1.  
    2. [FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]accX=MTbeapsisukimo2(:,9); [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]%X Acceleration
    3. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]accX=single(accX); [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% One Array
    4.  
    5. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]Fs=120; [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Sampling frequency
    6. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]t=0:1/Fs:22.945; [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Time vector of 22.945 seconds
    7. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]x=accX;
    8. nfft=2754; [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Length of FFT
    9. % Take fft, padding with zeros so that length(X)is equal to nfft
    10. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]X=fft(x,nfft);
    11. [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Take the magnitude of fft of x
    12. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]mx=abs(X);
    13. [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Frequency vector
    14. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]f=(0:nfft-1)*Fs/nfft;
    15. [/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22][FONT=Courier New][SIZE=2][COLOR=#228b22]% Generate the plot, title and labels.
    16. [/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]figure(1)
    17. plot(t,x)
    18. title([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Acceleration Wave Signal'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);
    19. xlabel([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Time (s)'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);
    20. ylabel([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Acceleration'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);
    21. figure(2)
    22. plot(f,mx)
    23. title([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Power Spectrum of a Acceleration Wave'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);
    24. xlabel([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Frequency (Hz)'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);
    25. ylabel([/SIZE][/FONT][/SIZE][/FONT][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0][FONT=Courier New][SIZE=2][COLOR=#a020f0]'Power'[/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][/COLOR][/SIZE][/FONT][FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2]);[/SIZE][/FONT][/SIZE][/FONT]
    26. [FONT=Courier New][SIZE=2][FONT=Courier New][SIZE=2][/SIZE][/FONT][/SIZE][/FONT]
    27.  
    I would be very thankfull for any consultation :)
     
    Last edited by a moderator: Jul 12, 2013
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