注：該代碼為慕課網課程中老師講解

            
              import pandas as pd
import numpy as np
import math
## 計算信息熵
def getEntropy(s):
    # 找到各個不同取值出現的次數
    if not isinstance(s, pd.core.series.Series):
        s = pd.Series(s)
    prt_ary = pd.groupby(s , by = s).count().values / float(len(s))
    return -(np.log2(prt_ary) * prt_ary).sum()
## 計算條件熵: 條件s1下s2的條件熵
def getCondEntropy(s1 , s2):
    d = dict()
    for i in list(range(len(s1))):
        d[s1[i]] = d.get(s1[i] , []) + [s2[i]]
    return sum([getEntropy(d[k]) * len(d[k]) / float(len(s1)) for k in d])


## 計算信息增益
def getEntropyGain(s1, s2):
    return getEntropy(s2) - getCondEntropy(s1, s2)

## 計算增益率
def getEntropyGainRadio(s1, s2):
    return getEntropyGain(s1, s2) / getEntropy(s2)


## 衡量離散值的相關性
import  math
def getDiscreteCorr(s1, s2):
    return getEntropyGain(s1,s2) / math.sqrt(getEntropy(s1) * getEntropy(s2))

# ######## 計算概率平方和
def getProbSS(s):
    if not isinstance(s, pd.core.series.Series):
        s = pd.Series(s)
    prt_ary = pd.groupby(s, by = s).count().values / float(len(s))
    return sum(prt_ary ** 2)
######## 計算基尼系數
def getGini(s1, s2):
    d = dict()
    for i in list(range(len(s1))):
        d[s1[i]] = d.get(s1[i] , []) + [s2[i]]
    return 1-sum([getProbSS(d[k]) * len(d[k]) / float(len(s1)) for k in d])
## 對離散型變量計算相關系數，并畫出熱力圖, 返回相關性矩陣
def DiscreteCorr(C_data):
    ## 對離散型變量(C_data)進行相關系數的計算
    C_data_column_names =  C_data.columns.tolist()
    ## 存儲C_data相關系數的矩陣
    import numpy as np
    dp_corr_mat = np.zeros([len(C_data_column_names) , len(C_data_column_names)])
    for i in range(len(C_data_column_names)):
        for j in range(len(C_data_column_names)):
            # 計算兩個屬性之間的相關系數
            temp_corr = getDiscreteCorr(C_data.iloc[:,i] , C_data.iloc[:,j])
            dp_corr_mat[i][j] = temp_corr
    # 畫出相關系數圖
    fig = plt.figure()
    fig.add_subplot(2,2,1)
    sns.heatmap(dp_corr_mat ,vmin= - 1, vmax= 1, cmap= sns.color_palette('RdBu' , n_colors= 128) , xticklabels= C_data_column_names , yticklabels= C_data_column_names)
    return pd.DataFrame(dp_corr_mat)

if __name__ == "__main__":
    s1 = pd.Series(['X1' , 'X1' , 'X2' , 'X2' , 'X2' , 'X2'])
    s2 = pd.Series(['Y1' , 'Y1' , 'Y1' , 'Y2' , 'Y2' , 'Y2'])
    print('CondEntropy:',getCondEntropy(s1, s2))
    print('EntropyGain:' , getEntropyGain(s1, s2))
    print('EntropyGainRadio' , getEntropyGainRadio(s1 , s2))
    print('DiscreteCorr:' , getDiscreteCorr(s1, s1))
    print('Gini' , getGini(s1, s2))