Why I could not convert time domain to frequency domain data?
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Hi all; i try tho covert the time domain to frequency domain by using fft function, but the acceleration vs Frequency plot is incorrect. So kindly can anyone explain what is the wrong in the code. Thanks in advance
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/161741/image.jpeg)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/161742/image.jpeg)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/161743/image.jpeg)
Lenght = size(x_time,2);
NFFT = 2^nextpow2(Lenght(1,1)-1); % Next power of 2 from length of b
Y1 = fft(Acc1,NFFT)/(Lenght(1,1)-1);
f = Fs/2*linspace(0,1,NFFT/2+1);
yPower1 = 2*abs(Y1(1:NFFT/2+1)); %magnitude
ydB1 = 20*log10(abs(Y1(1:NFFT/2+1))); %power
figure(51);
plot(f,yPower1);
xlabel('Frequency (Hz)','fontsize',14)
ylabel('Acc.','fontsize',14)
%axis ([0 10 0 10])
figure(61);
plot(f,ydB1);
xlabel('Frequency (Hz)','fontsize',14)
ylabel('Power (dB)','fontsize',14)
where x_time is the time vector Acc1 is the acceleration vector
4 comentarios
Star Strider
el 15 de Mzo. de 2017
That looks correct to me.
The details will be more apparent if you add this line after each plot:
set(gca, 'XLim',[0 30])
since there doesn’t appear to be anything above 30 Hz.
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