index1 = find_index(xf, 0.4)
index2 = find_index(xf, 1.6)
minyear = datetime.datetime.fromtimestamp(np.min(timeval)).year
maxyear = datetime.datetime.fromtimestamp(np.max(timeval)).year
plt.figure()
plt.title('Time and frequency_before')
plt.xlabel("Date")
plt.ylabel("Frequency (cycles/day)")
plt.imshow(yf[index1:index2, :], origin='lower', aspect='auto',
interpolation='nearest', extent=[minyear, maxyear, xf[index1], xf[index2]])
plt.colorbar()
結果圖：
http://imgur.com/gzvzPYo
minyear的值是2007
maxyear的值是2013
請問要如何不讓他變成指數型態呢??