#!/usr/bin/env python
# coding: utf-8

# # 크로스-엔트로피 비용

# [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/rickiepark/dl-illustrated/blob/master/notebooks/8-2.cross_entropy_cost.ipynb)

# 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(1, 0.9997)


# In[4]:


cross_entropy(1, 0.9)


# In[5]:


cross_entropy(1, 0.6)


# In[6]:


cross_entropy(1, 0.1192)


# In[7]:


cross_entropy(0, 0.1192)


# In[8]:


cross_entropy(1, 1-0.1192)