def featureExtract(S,fs): # Call power spectrum function and store P = powerSpectrum(S) # Loop to attain key harmonics thresh = 3 * numpy.mean(P) freqcount = 1 lenP = len(P) # Calculate Bandwidth of each freq bin HzPBin = fs / 2 / lenP # Define default values f1 = -1 Pf1 = -1 Pf2 = 1 Pf3 = -1 # The definition of a harmonic is a local maximum in the range for ic in numpy.arange(2,lenP-1): if (P[ic]>P[ic-1] and P[ic]>P[ic+1] and P[ic]>thresh): # First feature: Fundamental Frequency's Power if(freqcount==1): f1 = ic*HzPBin print f1 Pf1 = P[ic] elif(freqcount==2): f2 = ic*HzPBin Pf2 = P[ic] elif(freqcount==3): f3 = ic*HzPBin Pf3 = P[ic] freqcount += 1 # Second feature: Second Harmonic / FF ratio21 = Pf2 / Pf1 # Third feature: Third / Second Harmonic ratio32 = Pf3 / Pf2 # Fourth feature: Total power in first half of the spectrum # / total power in second half sum1=0.0 sum2=0.0 numP=len(P)/2.0 numP2 = int(numP) for ic in range(1,numP2): sum1 = sum1 + P[ic] sum2 = sum2 + P[ic+numP2] # Therefore, halfnhalf = sum1 / sum2 # Fifth feature: Center of Gravity Pbar = 0 Ptot = 0 for ibar in range(0,lenP): Pbar = Pbar + P[ibar]*ibar Ptot = Ptot + P[ibar] Pbar = (Pbar / Ptot)*fs/2/lenP # Sixth and final feature: Bandwidth BW = 0 P2tot = 0 for ibar2 in range(0,lenP): BW = BW + P[ibar2]*numpy.power((ibar2-Pbar),2) P2tot = P2tot + P[ibar2]*P[ibar2] BW = 2 * numpy.sqrt(BW / P2tot) BW = BW * fs/(2*lenP) #featV = [] featV = [f1,ratio21,ratio32,halfnhalf,Pbar,BW] return featV
# Purpose: call powerSpectrum and print out desired parameters from sim_data_def import sim_data from powerSpectrum_def import powerSpectrum # Define operating constants fs = 1000.0 # sample frequency Np = 256.0 # number of samples f = [10.0, 50.0,100.0] # signal frequency A = [1.0,0.4,0.4] # signal amplitude Ns = 3 # number of signals snr = 20.0 # signal to noise ratio (dB) # Store sim_data S = sim_data (fs, Np, f, A, Ns, snr) # Call powerSpectrum P = powerSpectrum (S) # Print out P's length print len(P) filename = "power_result.dat" file = open(filename,"w") for x in range(1,len(P)): txt = str(P[x]) + "\n" file.write(txt) file.close()
