In [1]:

    

from numpy import log


    

In [2]:

    

def cross_entropy(y, a):
    return -1*(y*log(a) + (1-y)*log(1-a))


    

In [3]:

    

cross_entropy(0, 0.1)


    

    
Out[3]:





0.10536051565782628

In [4]:

    

cross_entropy(0, 0.01)


    

    
Out[4]:





0.010050335853501451

In [5]:

    

cross_entropy(1, 0.99)


    

    
Out[5]:





0.010050335853501451

In [6]:

    

cross_entropy(0, 0.3)


    

    
Out[6]:





0.35667494393873245

In [7]:

    

cross_entropy(0, 0.6)


    

    
Out[7]:





0.916290731874155

In [8]:

    

cross_entropy(0, 0.9)


    

    
Out[8]:





2.3025850929940459

In [ ]: