minima_maxima_noisy_spectrum.py

# see http://stackoverflow.com/a/20642478/1435167
import numpy as np
from scipy.signal import argrelextrema

x = np.random.random(100)

# for local maxima
argrelextrema(x, np.greater)

# for local minima
argrelextrema(x, np.less)

ind = np.arange(0,len(x))

# see http://wiki.scipy.org/Cookbook/SavitzkyGolay
smo = savitzky_golay(savitzky_golay(x,21,3),21,3)

plt.plot(ind,x,'--')
#plt.plot(ind[argrelextrema(x, np.greater)],x[argrelextrema(x, np.greater)],'bo')
plt.plot(ind,smo,'r',lw=3)
# maxima
plt.plot(ind[argrelextrema(smo, np.greater)],smo[argrelextrema(smo, np.greater)],'ro')
# minima
plt.plot(ind[argrelextrema(smo, np.less)],smo[argrelextrema(smo, np.less)],'bo')
plt.ylim([-.5,1.5])