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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:
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
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:
MergeDat=MergeDat.merge(Motor,how="left") print(MergeDat) where MergeDat= df1 and Motor= df2
As result it returns:
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...
Appreciate any help!
807
To merge two Pandas DataFrame with common column, use the merge() function and set the ON parameter as the column name. To set NaN for unmatched values, use the “how” parameter and set it left or right. That would mean, merging left or right.
The merge() method updates the content of two DataFrame by merging them together, using the specified method(s). Use the parameters to control which values to keep and which to replace.
left_on − Columns from the left DataFrame to use as keys. Can either be column names or arrays with length equal to the length of the DataFrame. right_on − Columns from the right DataFrame to use as keys. Can either be column names or arrays with length equal to the length of the DataFrame.
The concat() function can be used to concatenate two Dataframes by adding the rows of one to the other. The merge() function is equivalent to the SQL JOIN clause. 'left', 'right' and 'inner' joins are all possible.
You need same dtype of joined columns:
#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") If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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