pandas groupby (TimeGrouper)重写Q3

import osimport pandas as pdimport datetimeroot = 'D:/select_files'all_sudu = pd.DataFrame()all_time = []for every_file in os.listdir(root):#每个文件取一列    df=pd.read_csv(os.path.join(root,every_file),sep=',').iloc[:,3].replace('/////',np.nan)    #print df#解析文件名中所包含的日期并转换为datatime格式        time_index = pd.to_datetime(every_file.split('_')[4])    #print time_index    all_time.append(time_index)    all_sudu = all_sudu.append(df, ignore_index=True)#把time作为indexall_sudu.index = all_time#print all_sudu#生成日期范围rng = pd.date_range(start = '20130629020000', end = '20130629030000', freq='5min')#print rng#reindex从而实现日期范围内未有的部分全部插空值all_time_sudu = all_sudu.reindex(rng)#分组级运算和转换def demean(arr):    return arr-arr.mean()demeaned = all_time_sudu.groupby(pd.TimeGrouper(freq='15min')).transform(demean)print demeaned