pandas 将熊猫系列从字符串转换为唯一的 int id
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Convert pandas series from string to unique int ids
提问by Dave Novelli
I have a categorical variable in a series. I want to assign integer ids to each unique value and create a new series with the ids, effectively turning a string variable into an integer variable. What is the most compact/efficient way to do this?
我有一个系列中的分类变量。我想为每个唯一值分配整数 id，并使用 id 创建一个新系列，有效地将字符串变量转换为整数变量。执行此操作的最紧凑/最有效的方法是什么？
回答by unutbu
You could use pandas.factorize:
你可以使用pandas.factorize：
In [32]: s = pd.Series(['a','b','c'])
In [33]: labels, levels = pd.factorize(s)
In [35]: labels
Out[35]: array([0, 1, 2])
回答by Daniel Golden
Example using the new pandas categoricaltype in pandas 0.15+
categorical在 pandas 0.15+ 中使用新的 pandas类型的示例
http://pandas.pydata.org/pandas-docs/version/0.16.2/categorical.html
http://pandas.pydata.org/pandas-docs/version/0.16.2/categorical.html
In [553]: x = pd.Series(['a', 'a', 'a', 'b', 'b', 'c']).astype('category')
In [554]: x
Out[554]:
0 a
1 a
2 a
3 b
4 b
5 c
dtype: category
Categories (3, object): [
a
, b
, c]
In [555]: x.cat.codes
Out[555]:
0 0
1 0
2 0
3 1
4 1
5 2
dtype: int8
