Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


sam
Posts:
16
Registered:
2/20/13


FFT of an array
Posted:
Mar 7, 2013 11:00 AM


Hi
I'm simply trying to plot a FFT of an array. I can take an FFT and get the correct shape but cannot scale to correct frequencies. Can anyone please help me? i've tried various methods but i'm not getting very far. My code is as follows:
 [t, x]=ode45(@vanderpol,0:2*pi/OMEG:1000,[0 1]);
A = size(x); Fs = (2*pi/OMEG)/1000; %sampling freq  because ODE from t =0:2*pi/OMEG:1000 NFFT = 2^nextpow2(A); output = fft(x,NFFT)/A; freq = Fs/2*linspace(0,1,NFFT/2+1); figure(1) plot(freq, 2*abs(output(1:NFFT/2+1))) 
where t = 90000x1 double, x = 90000x2 double, a = 90000x2 complex double
Anyhelp would be greatly appreciated. I've been going round in circles for ages.



