Plotting of FRF curves
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I want to plot FRF vs Frequency graph.I have a matrix 'a' of acceleration & a force matrix 'f' both of 30000X1 size, collected in 3secs with a time step of 0.0001 sec.I am using the following steps to plot FRF. a=[ ]; f=[ ]; ffa=fft(a); fff = fft(f); frf, H=ffa./fff; aH =abs(H); I want to plot FRF vs Frequency graph using log(aH) on Y-axis. Pl tell me how to specify x-axis?
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bym
2011-6-29
Frequency resolution is sampling frequency divided by FFT points. So for a one sided spectrum, it is (directly from the documentation)
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
you can then plot as
semilogy(f,aH)
or
loglog(f,aH)
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