Python Pandas Merge 返回 NaN
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Pandas Merge returns NaN
提问by 2Obe
I have issues with the merging of two large Dataframes since the merge returns NaN values though there are fitting values. The two dfs are shaped like:
我在合并两个大数据帧时遇到问题，因为尽管存在拟合值，但合并返回 NaN 值。这两个 dfs 的形状如下：
df1
df1
Motor
2232
1524
2230
2230
2224
1516
1724
2224
1524
1624
1724
2224
2224
1524
1524
1516
1524
2224
1624
1724
1724
2224
2224
df2
df2
Motor Output Torque (mNm)
0615 0,17
1219 0,72
1516 0,59
1624 2
2230 4,7
2233 5,9
0816 0,7
1016 0,92
1024 1,6
1224 1,7
1319 1,4
1331 3,8
1516 0,97
1524 2,9
1717 2,2
1724 4,5
2224 6,8
2232 10
1336 3,6
1727 4,9
1741 8,8
2237 12
2642 26
I use the code:
我使用代码：
MergeDat=MergeDat.merge(Motor,how="left")
print(MergeDat)
where MergeDat= df1 and Motor= df2
其中 MergeDat= df1 和 Motor= df2
As resultit returns:
作为结果返回：
Motor Output Torque (mNm)
0 2232 NaN
1 1524 NaN
2 2230 NaN
3 2230 NaN
4 2224 NaN
5 1516 NaN
6 1724 NaN
7 2224 NaN
8 1524 NaN
9 1624 NaN
10 1724 NaN
11 2224 NaN
12 2224 NaN
13 1524 NaN
14 1524 NaN
15 1516 NaN
16 1524 NaN
17 2224 NaN
18 1624 NaN
19 1724 NaN
20 1724 NaN
21 2224 NaN
22 2224 NaN
23 1524 NaN
24 1724 NaN
25 1841 NaN
26 2224 NaN
I have no idea why the Output Torque column is not merged...
我不知道为什么输出扭矩列没有合并......
Appreciate any help!
感谢任何帮助！
回答by jezrael
You need same dtypeof joined columns:
您需要相同dtype的连接列：
#convert first or second to str or int
MergeDat['Motor'] = MergeDat['Motor'].astype(str)
#Motor['Motor'] = Motor['Motor'].astype(str)
#MergeDat['Motor'] = MergeDat['Motor'].astype(int)
Motor['Motor'] = Motor['Motor'].astype(int)
#convert first or second to str or int
#MergeDat['Motor'] = MergeDat['Motor'].astype(str)
Motor['Motor'] = Motor['Motor'].astype(str)
MergeDat['Motor'] = MergeDat['Motor'].astype(int)
#Motor['Motor'] = Motor['Motor'].astype(int)
MergeDat=MergeDat.merge(Motor,how="left")
