# Acceleration vs Time data into FFT

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nur yusof il 17 Gen 2015
Commentato: nur yusof il 21 Gen 2015
I have acceleration vs time data. I want to get FFT value from the data.Can someone show me the way?
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### Risposta accettata

Image Analyst il 17 Gen 2015
spectrum = fft(signal);
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nur yusof il 18 Gen 2015
I import the data into matlab. Thats means the coding should be spectrum = fft(signal); plot(1:N,abs (spectrum));
Is it true??
nur yusof il 21 Gen 2015
I got the FFT value from your coding image analyst.Is the bandwidth of FFT data according to my time history domain data?If not,how to ensure the bandwidth is within the interval?Can you brief me about the coding? My bandwidth range is 50Hz-500Hz from time domain history data.

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### Più risposte (1)

Shoaibur Rahman il 17 Gen 2015
Define the number of DFT points N, and then perform the fft.
N = pow2(nextpow2(length(signal)));
y = fft(signal,N);
plot(1:N,abs(y))
If the length of your signal is a big number then set the value of N manually to a lower value, like N = 64, 128, 256, etc. This will make your figure to look better sometime, but note that that may not be accurate always from the computational point of view.
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nur yusof il 18 Gen 2015
Attached previous figure is solve by Shoaibur's coding. While, attached figure solve by image analyst.I dont know why the figure look like that.I think the frequency solve by Shoaibur is high maybe due to the the vibration of bridge,vehicle and noise from environment.So, it has high value.
nur yusof il 21 Gen 2015
I got the FFT value from the coding.Is the bandwidth of FFT data according to my time history domain data?If not,how to ensure the bandwidth is within the interval?Can you brief me about the coding? My bandwidth range is 50Hz-500Hz from time domain history data.

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