45 x2 = np.linspace(mu - 3*sig, mu + 3*sig, 100)
 46
 47 n, x, _ = plt.hist(vlist, bins=np.linspace(xmin, xmax, binnum),
 48                            histtype=u'step', normed=False, color = 'black',linewidth=4)
 49 binwidth = x[1]-x[0]
 50 plt.plot(x2,binwidth*len(vlist)*mlab.normpdf(x2, mu, sig),color = 'red', linewidth = 4)