pandas 合并返回空数据框 [英] Pandas merge return empty dataframe

问题描述

我有两个数据框

current_bin.info()    
<class 'pandas.core.frame.DataFrame'>
Int64Index: 16 entries, 0 to 15
Data columns (total 3 columns):
id               16 non-null object
fpd              16 non-null float64
avgSpeedBinID    16 non-null object
dtypes: float64(1), object(2)

current_bin数据帧如下:

the current_bin data frame looks like:

current_bin
    id          fpd         avgSpeedBinID
0   1.1.4.1     2.818623    1
1   1.1.4.10    0.266681    10
2   1.1.4.11    0.250017    11
3   1.1.4.12    0.234749    12
4   1.1.4.13    0.222515    13
5   1.1.4.14    0.216150    14
6   1.1.4.15    0.218368    15
7   1.1.4.16    0.227663    16
8   1.1.4.2     1.475454    2
9   1.1.4.3     0.805842    3
10  1.1.4.4     0.581797    4
11  1.1.4.5     0.450314    5
12  1.1.4.6     0.379107    6
13  1.1.4.7     0.335155    7
14  1.1.4.8     0.305992    8
15  1.1.4.9     0.284210    9

和

avg.info()
<class 'pandas.core.frame.DataFrame'>
Int64Index: 16 entries, 0 to 15
Data columns (total 4 columns):
avgSpeedBinID      16 non-null int64
avgBinSpeed        16 non-null float64
avgSpeedBinDesc    16 non-null object
temp               16 non-null int64
dtypes: float64(1), int64(2), object(1)

如下所示:

    avgSpeedBinID   avgBinSpeed avgSpeedBinDesc             temp
0   1               3           speed < 2.5mph              0
1   2               5           2.5mph <= speed < 7.5mph    0
2   3               10          7.5mph <= speed < 12.5mph   0
3   4               15          12.5mph <= speed < 17.5mph  0
4   5               20          17.5mph <= speed <22.5mph   0
5   6               25          22.5mph <= speed < 27.5mph  0
6   7               30          27.5mph <= speed < 32.5mph  0
7   8               35          32.5mph <= speed < 37.5mph  0
8   9               40          37.5mph <= speed < 42.5mph  0
9   10              45          42.5mph <= speed < 47.5mph  0
10  11              50          47.5mph <= speed < 52.5mph  0
11  12              55          52.5mph <= speed < 57.5mph  0
12  13              60          57.5mph <= speed < 62.5mph  0
13  14              65          62.5mph <= speed < 67.5mph  0
14  15              70          67.5mph <= speed < 72.5mph  0
15  16              75          72.5mph <= speed            0

两个数据帧在avgSpeedBinID字段上的值都为1到16，但是当我尝试将数据帧合并在一起时

both dataframes have a value 1 to 16 on the avgSpeedBinID field, however, when i try to merge the data frames together

avg.merge(current_bin, on='avgSpeedBinID')

我得到一个空数据框

avgSpeedBinID   avgBinSpeed avgSpeedBinDesc temp    id  fpd

为什么会发生这种情况，我该如何解决该问题?

Why is this happening and how can i correct the problem?

推荐答案

当前bin数据帧中的avgSpeedBinID类型为str，而avg中的类型为int. 只需将str强制转换为int，合并将起作用.

The avgSpeedBinID in the current bin dataframe is type str and in avg is int. Just cast the str one into an int and the merge will work.

current_bin['avgSpeedBinID'] = current_bin['avgSpeedBinID'].astype(int)

avg.merge(current_bin, on='avgSpeedBinID')


    avgSpeedBinID   avgBinSpeed avgSpeedBinDesc             temp    id   fpd
0   1               3            speed < 2.5mph             0   1.1.4.1  2.818623
1   2               5            2.5mph <= speed < 7.5mph   0   1.1.4.2  1.475454
2   3               10           7.5mph <= speed < 12.5mph  0   1.1.4.3  0.805842
3   4               15           12.5mph <= speed < 17.5mph 0   1.1.4.4  0.581797
4   5               20           17.5mph <= speed <22.5mph  0   1.1.4.5  0.450314
5   6               25           22.5mph <= speed < 27.5mph 0   1.1.4.6  0.379107
6   7               30           27.5mph <= speed < 32.5mph 0   1.1.4.7  0.335155
7   8               35           32.5mph <= speed < 37.5mph 0   1.1.4.8  0.305992  
8   9               40           37.5mph <= speed < 42.5mph 0   1.1.4.9  0.284210
9   10              45           42.5mph <= speed < 47.5mph 0   1.1.4.10 0.266681
10  11              50           47.5mph <= speed < 52.5mph 0   1.1.4.11 0.250017
11  12              55           52.5mph <= speed < 57.5mph 0   1.1.4.12 0.234749
12  13              60           57.5mph <= speed < 62.5mph 0   1.1.4.13 0.222515
13  14              65           62.5mph <= speed < 67.5mph 0   1.1.4.14 0.216150
14  15              70           67.5mph <= speed < 72.5mph 0   1.1.4.15 0.218368
15  16              75           72.5mph <= speed           0   1.1.4.16 0.22763

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