How to get the first column of a pandas DataFrame as a Series?
PythonDataframePandasSeriesPython Problem Overview
I tried:
x=pandas.DataFrame(...)
s = x.take([0], axis=1)
And s gets a DataFrame, not a Series.
Python Solutions
Solution 1 - Python
>>> import pandas as pd
>>> df = pd.DataFrame({'x' : [1, 2, 3, 4], 'y' : [4, 5, 6, 7]})
>>> df
x y
0 1 4
1 2 5
2 3 6
3 4 7
>>> s = df.ix[:,0]
>>> type(s)
<class 'pandas.core.series.Series'>
>>>
===========================================================================
UPDATE
If you're reading this after June 2017, ix has been deprecated in pandas 0.20.2, so don't use it. Use loc or iloc instead. See comments and other answers to this question.
Solution 2 - Python
From v0.11+, ... use df.iloc.
In [7]: df.iloc[:,0]
Out[7]:
0 1
1 2
2 3
3 4
Name: x, dtype: int64
Solution 3 - Python
You can get the first column as a Series by following code:
x[x.columns[0]]
Solution 4 - Python
Isn't this the simplest way?
By column name:
In [20]: df = pd.DataFrame({'x' : [1, 2, 3, 4], 'y' : [4, 5, 6, 7]})
In [21]: df
Out[21]:
x y
0 1 4
1 2 5
2 3 6
3 4 7
In [23]: df.x
Out[23]:
0 1
1 2
2 3
3 4
Name: x, dtype: int64
In [24]: type(df.x)
Out[24]:
pandas.core.series.Series
Solution 5 - Python
This works great when you want to load a series from a csv file
x = pd.read_csv('x.csv', index_col=False, names=['x'],header=None).iloc[:,0]
print(type(x))
print(x.head(10))
<class 'pandas.core.series.Series'>
0 110.96
1 119.40
2 135.89
3 152.32
4 192.91
5 177.20
6 181.16
7 177.30
8 200.13
9 235.41
Name: x, dtype: float64
Solution 6 - Python
df[df.columns[i]]
where i is the position/number of the column(starting from 0).
So, i = 0 is for the first column.
You can also get the last column using i = -1