In [1]:
#Visualize Log Loss when True value = 1
#y-axis is log loss, x-axis is probabilty that label = 1
#As you can see Log Loss increases rapidly as we approach 0
#But increases slowly as our predicted probability gets closer to 1
import matplotlib.pyplot as plt
import numpy as np
from sklearn.metrics import log_loss

x = [i*.0001 for i in range(1,10000)] # 10000
y = [log_loss([0,1 if i > 0 else 0],[[0.0001, 0.9999],[1-(i*.0001), i*.0001]],eps=1e-15) for i in range(1,10000,1)]

plt.plot(x, y)
plt.axis([-.05, 1.1, -.8, 10])
plt.title("Log Loss when true label = 1")
plt.xlabel("predicted probability")
plt.ylabel("log loss")

plt.show()
In [2]:
x = [i*.0001 for i in range(1,10000)]
y = [log_loss([1],[[i*.0001,1-(i*.0001)]],eps=1e-15) for i in range(1,10000,1)]

plt.plot(x, y)
plt.axis([-.05, 1.1, -.8, 10])
plt.title("Log Loss when true label = 1")
plt.xlabel("predicted probability")
plt.ylabel("log loss")

plt.show()
------------------------------------------------------------------
ValueError                       Traceback (most recent call last)
<ipython-input-2-4b3d43fb690a> in <module>()
      1 x = [i*.0001 for i in range(1,10000)]
----> 2 y = [log_loss([1],[[i*.0001,1-(i*.0001)]],eps=1e-15) for i in range(1,10000,1)]
      3 
      4 plt.plot(x, y)
      5 plt.axis([-.05, 1.1, -.8, 10])

/Users/Natsume/miniconda2/envs/ml/lib/python2.7/site-packages/sklearn/metrics/classification.pyc in log_loss(y_true, y_pred, eps, normalize, sample_weight, labels)
   1620             raise ValueError('y_true contains only one label ({0}). Please '
   1621                              'provide the true labels explicitly through the '
-> 1622                              'labels argument.'.format(lb.classes_[0]))
   1623         else:
   1624             raise ValueError('The labels array needs to contain at least two '

ValueError: y_true contains only one label (1). Please provide the true labels explicitly through the labels argument.
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