Question

我有2个数据框，第一个在“ station_anal”下方

        count   Start station number
index       
31623   17105   31623
31258   11432   31258
31201   10194   31201
31200   9505    31200
31247   9145    31247

第二个数据帧“ vt”是：

    Start station number    Start station
0   31214                   17th & Corcoran St NW
1   31104                   Adams Mill & Columbia Rd NW
2   31221                   18th & M St NW
3   31111                   10th & U St NW
4   31260                    23rd & E St NW

station_anal的尺寸为486x2

vt大小为8000x2

我的左连接命令是：

lj = pd.merge(station_anal, vt, how = 'left', on = 'Start station number')

dtypes对于两列都相同，即int64

但是lj返回：

lj.head()

count   Start station number    Start station
0   17105   31623   Columbus Circle / Union Station
1   17105   31623   Columbus Circle / Union Station
2   17105   31623   Columbus Circle / Union Station
3   17105   31623   Columbus Circle / Union Station
4   17105   31623   Columbus Circle / Union Station

大小为8000x3

毫无意义，因为我的理解是左连接，在这种情况下，结果矩阵行大小始终是第一个数据帧486

Answer 1

让我们使用地图：

station_anal ['起始站号'] = station_anal ['起始站号']
.map（vt.set_index（'起始站Numer'）['起始站']）

更新放置的重复项，然后映射：

mapper = vt.drop_duplicates('Start Station Number')\
           .set_index('Start station number')['Start station']

station_anal['Start Station'] = station_anal['Start station number']\
                                     .map(mapper)

熊猫左联接返回更大的矩阵并且不起作用

1 个答案: