How to create a column and reindex in pandas?
I'm a new pandas learner. I have 5 rows dataframe as follow:
A B C D
0 2.34 3.16 99.0 3.2
1 2.1 55.5 77.5 1
2 22.1 54 89 33
3 23 1.24 4.7 5
4 45 2.5 8.7 99
I want to replace index column 0,1...4 with new index 1 to 5. My expected output is:
A B C D
1 2.34 3.16 99.0 3.2
2 2.1 55.5 77.5 1
3 22.1 54 89 33
4 23 1.24 4.7 5
5 45 2.5 8.7 99
What I did is I create a new column:
new_index = pd.DataFrame({'#': range(1, 5 + 1 ,1)})
Then I tried to reindex:
df.reindex(new_index)
But I got error:
ValueError: Buffer has wrong number of dimensions (expected 1, got 2)
What should I do to reindex the former index? Thanks.
Use set_index
In [5081]: df.set_index([range(1, 6)])
Out[5081]:
A B C D
1 2.34 3.16 99.0 3.2
2 2.10 55.50 77.5 1.0
3 22.10 54.00 89.0 33.0
4 23.00 1.24 4.7 5.0
5 45.00 2.50 8.7 99.0
Or set values of df.index
In [5082]: df.index = range(1, 6)
In [5083]: df
Out[5083]:
A B C D
1 2.34 3.16 99.0 3.2
2 2.10 55.50 77.5 1.0
3 22.10 54.00 89.0 33.0
4 23.00 1.24 4.7 5.0
5 45.00 2.50 8.7 99.0
Details
Original df
In [5085]: df
Out[5085]:
A B C D
0 2.34 3.16 99.0 3.2
1 2.10 55.50 77.5 1.0
2 22.10 54.00 89.0 33.0
3 23.00 1.24 4.7 5.0
4 45.00 2.50 8.7 99.0