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import numpy as np import pandas as pd def SplitData(df, col, numOfSplit, special_attribute=[]): ''' :param df: 按照col排序后的数据集 :param col: 待分箱的变量 :param numOfSplit: 切分的组别数 :param special_attribute: 在切分数据集的时候，某些特殊值需要排除在外 :return: 在原数据集上增加一列，把原始细粒度的col重新划分成粗粒度的值，便于分箱中的合并处理 ''' df2 = df.copy() if special_attribute != []: df2 = df.loc[~df[col].isin(special_attribute)] N = df2.shape[0] n = int(N/numOfSplit) splitPointIndex = [i*n for i in range(1,numOfSplit)] rawValues = sorted(list(df2[col])) splitPoint = [rawValues[i] for i in splitPointIndex] splitPoint = sorted(list(set(splitPoint))) return splitPoint # def Chi2(df, total_col, bad_col, overallRate): # ''' # :param df: 包含全部样本总计与坏样本总计的数据框 # :param total_col: 全部样本的个数 # :param bad_col: 坏样本的个数 # :param overallRate: 全体样本的坏样本占比 # :return: 卡方值 # ''' # df2 = df.copy() # # 期望坏样本个数＝全部样本个数*平均坏样本占比 # df2['expected'] = df[total_col].apply(lambda x: x*overallRate) # combined = zip(df2['expected'], df2[bad_col]) # chi = [(i[0]-i[1])**2/i[0] for i in combined] # chi2 = sum(chi) # return chi2 def Chi2(df, total_col, bad_col): ''' :param df: 包含全部样本总计与坏样本总计的数据框 :param total_col: 全部样本的个数 :param bad_col: 坏样本的个数 :return: 卡方值 ''' df2 = df.copy() # 求出df中，总体的坏样本率和好样本率 badRate = sum(df2[bad_col])*1.0/sum(df2[total_col]) # 当全部样本只有好或者坏样本时，卡方值为0 if badRate in [0,1]: return 0 df2['good'] = df2.apply(lambda x: x[total_col] - x[bad_col], axis = 1) goodRate = sum(df2['good']) * 1.0 / sum(df2[total_col]) # 期望坏（好）样本个数＝全部样本个数*平均坏（好）样本占比 df2['badExpected'] = df[total_col].apply(lambda x: x*badRate) df2['goodExpected'] = df[total_col].apply(lambda x: x * goodRate) badCombined = zip(df2['badExpected'], df2[bad_col]) goodCombined = zip(df2['goodExpected'], df2['good']) badChi = [(i[0]-i[1])**2/i[0] for i in badCombined] goodChi = [(i[0] - i[1]) ** 2 / i[0] for i in goodCombined] chi2 = sum(badChi) + sum(goodChi) return chi2 # Chi2 的另外一种计算方法 # def Chi2(df, total_col, bad_col): # df2 = df.copy() # df2['good'] = df2[total_col] - df2[bad_col] # goodTotal = sum(df2['good']) # badTotal = sum(df2[bad_col]) # p1 = df2.loc[0]['good']*1.0/df2.loc[0][total_col] # p2 = df2.loc[1]['good']*1.0/df2.loc[1][total_col] # w1 = df2.loc[0]['good']*1.0/goodTotal # w2 = df2.loc[0][bad_col]*1.0/badTotal # N = sum(df2[total_col]) # return N*(p1-p2)*(w1-w2) def BinBadRate(df, col, target, grantRateIndicator=0): ''' :param df: 需要计算好坏比率的数据集 :param col: 需要计算好坏比率的特征 :param target: 好坏标签 :param grantRateIndicator: 1返回总体的坏样本率，0不返回 :return: 每箱的坏样本率，以及总体的坏样本率（当grantRateIndicator＝＝1时） ''' total = df.groupby([col])[target].count() total = pd.DataFrame({'total': total}) bad = df.groupby([col])[target].sum() bad = pd.DataFrame({'bad': bad}) regroup = total.merge(bad, left_index=True, right_index=True, how='left') regroup.reset_index(level=0, inplace=True) regroup['bad_rate'] = regroup.apply(lambda x: x.bad * 1.0 / x.total, axis=1) dicts = dict(zip(regroup[col],regroup['bad_rate'])) if grantRateIndicator==0: return (dicts, regroup) N = sum(regroup['total']) B = sum(regroup['bad']) overallRate = B * 1.0 / N return (dicts, regroup, overallRate) ### ChiMerge_MaxInterval: split the continuous variable using Chi-square value by specifying the max number of intervals def ChiMerge(df, col, target, max_interval=5,special_attribute=[],minBinPcnt=0): ''' :param df: 包含目标变量与分箱属性的数据框 :param col: 需要分箱的属性 :param target: 目标变量，取值0或1 :param max_interval: 最大分箱数。如果原始属性的取值个数低于该参数，不执行这段函数 :param special_attribute: 不参与分箱的属性取值 :param minBinPcnt：最小箱的占比，默认为0 :return: 分箱结果 ''' colLevels = sorted(list(set(df[col]))) N_distinct = len(colLevels) if N_distinct <= max_interval: #如果原始属性的取值个数低于max_interval，不执行这段函数 print ("The number of original levels for {} is less than or equal to max intervals".format(col)) return colLevels[:-1] else: if len(special_attribute)>=1: df1 = df.loc[df[col].isin(special_attribute)] df2 = df.loc[~df[col].isin(special_attribute)] else: df2 = df.copy() N_distinct = len(list(set(df2[col]))) # 步骤一: 通过col对数据集进行分组，求出每组的总样本数与坏样本数 if N_distinct > 100: split_x = SplitData(df2, col, 100) df2['temp'] = df2[col].map(lambda x: AssignGroup(x, split_x)) else: df2['temp'] = df2[col] # 总体bad rate将被用来计算expected bad count (binBadRate, regroup, overallRate) = BinBadRate(df2, 'temp', target, grantRateIndicator=1) # 首先，每个单独的属性值将被分为单独的一组 # 对属性值进行排序，然后两两组别进行合并 colLevels = sorted(list(set(df2['temp']))) groupIntervals = [[i] for i in colLevels] # 步骤二：建立循环，不断合并最优的相邻两个组别，直到： # 1，最终分裂出来的分箱数<＝预设的最大分箱数 # 2，每箱的占比不低于预设值（可选） # 3，每箱同时包含好坏样本 # 如果有特殊属性，那么最终分裂出来的分箱数＝预设的最大分箱数－特殊属性的个数 split_intervals = max_interval - len(special_attribute) while (len(groupIntervals) > split_intervals): # 终止条件: 当前分箱数＝预设的分箱数 # 每次循环时, 计算合并相邻组别后的卡方值。具有最小卡方值的合并方案，是最优方案 chisqList = [] for k in range(len(groupIntervals)-1): temp_group = groupIntervals[k] + groupIntervals[k+1] df2b = regroup.loc[regroup['temp'].isin(temp_group)] #chisq = Chi2(df2b, 'total', 'bad', overallRate) chisq = Chi2(df2b, 'total', 'bad') chisqList.append(chisq) best_comnbined = chisqList.index(min(chisqList)) groupIntervals[best_comnbined] = groupIntervals[best_comnbined] + groupIntervals[best_comnbined+1] # after combining two intervals, we need to remove one of them groupIntervals.remove(groupIntervals[best_comnbined+1]) groupIntervals = [sorted(i) for i in groupIntervals] cutOffPoints = [max(i) for i in groupIntervals[:-1]] # 检查是否有箱没有好或者坏样本。如果有，需要跟相邻的箱进行合并，直到每箱同时包含好坏样本 groupedvalues = df2['temp'].apply(lambda x: AssignBin(x, cutOffPoints)) df2['temp_Bin'] = groupedvalues (binBadRate,regroup) = BinBadRate(df2, 'temp_Bin', target) [minBadRate, maxBadRate] = [min(binBadRate.values()),max(binBadRate.values())] while minBadRate ==0 or maxBadRate == 1: # 找出全部为好／坏样本的箱 indexForBad01 =