python中虚拟变量之间的交互
我试图理解在使用python中虚拟变量之间的交互,python,pandas,data-science,Python,Pandas,Data Science,我试图理解在使用get\u dummies后如何寻址列。 例如,假设我有三个分类变量。 第一个变量有两个级别。 第二个变量有5个级别。 第三个变量有两个级别 df=pd.DataFrame({"a":["Yes","Yes","No","No","No","Yes","Yes"], "b":["a","b","c","d","e","a","c"],"c":["1","2","2","1","2","1","1"]}) 我为这三个变量创建了假人,以便在python的sklearn回归中使用它们
get\u dummies
后如何寻址列。
例如,假设我有三个分类变量。
第一个变量有两个级别。
第二个变量有5个级别。
第三个变量有两个级别
df=pd.DataFrame({"a":["Yes","Yes","No","No","No","Yes","Yes"], "b":["a","b","c","d","e","a","c"],"c":["1","2","2","1","2","1","1"]})
我为这三个变量创建了假人,以便在python的sklearn
回归中使用它们
df1 = pd.get_dummies(df,drop_first=True)
现在我想创建两个交互(乘法):bc,ba
如何创建每个dummies变量与另一个变量之间的乘法,而不使用它们的特定名称:
df1['a_yes_b'] = df1['a_Yes']*df1['b_b']
df1['a_yes_c'] = df1['a_Yes']*df1['b_c']
df1['a_yes_d'] = df1['a_Yes']*df1['b_d']
df1['a_yes_e'] = df1['a_Yes']*df1['b_e']
df1['c_2_b'] = df1['c_2']*df1['b_b']
df1['c_2_c'] = df1['c_2']*df1['b_c']
df1['c_2_d'] = df1['c_2']*df1['b_d']
df1['c_2_e'] = df1['c_2']*df1['b_e']
谢谢。您可以使用循环来创建新列,因为可以使用和筛选列名: 但是如果
a
和b
只有一列(在示例中是,在实际数据中可能是),则使用:,并且:
您可以将dataframe列转换为numpy数组,然后将其相应地相乘。以下是您可以找到实现此目的的方法的链接:
这解决了您的问题:
def get_design_with_pair_interaction(data, group_pair):
""" Get the design matrix with the pairwise interactions
Parameters
----------
data (pandas.DataFrame):
Pandas data frame with the two variables to build the design matrix of their two main effects and their interaction
group_pair (iterator):
List with the name of the two variables (name of the columns) to build the design matrix of their two main effects and their interaction
Returns
-------
x_new (pandas.DataFrame):
Pandas data frame with the design matrix of their two main effects and their interaction
"""
x = pd.get_dummies(data[group_pair])
interactions_lst = list(
itertools.combinations(
x.columns.tolist(),
2,
),
)
x_new = x.copy()
for level_1, level_2 in interactions_lst:
if level_1.split('_')[0] == level_2.split('_')[0]:
continue
x_new = pd.concat(
[
x_new,
x[level_1] * x[level_2]
],
axis=1,
)
x_new = x_new.rename(
columns = {
0: (level_1 + '_' + level_2)
}
)
return x_new
a = df1.filter(regex='^a')
b = df1.filter(regex='^b')
c = df1.filter(regex='^c')
dfa = b.mul(a.squeeze(), axis=0).rename(columns=lambda x: a.columns[0] + x[1:])
dfc = b.mul(c.squeeze(), axis=0).rename(columns=lambda x: c.columns[0] + x[1:])
df1 = pd.concat([df1, dfa, dfc], axis=1)
print (df1)
a_Yes b_b b_c b_d b_e c_2 a_Yes_b a_Yes_c a_Yes_d a_Yes_e c_2_b \
0 1 0 0 0 0 0 0 0 0 0 0
1 1 1 0 0 0 1 1 0 0 0 1
2 0 0 1 0 0 1 0 0 0 0 0
3 0 0 0 1 0 0 0 0 0 0 0
4 0 0 0 0 1 1 0 0 0 0 0
5 1 0 0 0 0 0 0 0 0 0 0
6 1 0 1 0 0 0 0 1 0 0 0
c_2_c c_2_d c_2_e
0 0 0 0
1 0 0 0
2 1 0 0
3 0 0 0
4 0 0 1
5 0 0 0
6 0 0 0
def get_design_with_pair_interaction(data, group_pair):
""" Get the design matrix with the pairwise interactions
Parameters
----------
data (pandas.DataFrame):
Pandas data frame with the two variables to build the design matrix of their two main effects and their interaction
group_pair (iterator):
List with the name of the two variables (name of the columns) to build the design matrix of their two main effects and their interaction
Returns
-------
x_new (pandas.DataFrame):
Pandas data frame with the design matrix of their two main effects and their interaction
"""
x = pd.get_dummies(data[group_pair])
interactions_lst = list(
itertools.combinations(
x.columns.tolist(),
2,
),
)
x_new = x.copy()
for level_1, level_2 in interactions_lst:
if level_1.split('_')[0] == level_2.split('_')[0]:
continue
x_new = pd.concat(
[
x_new,
x[level_1] * x[level_2]
],
axis=1,
)
x_new = x_new.rename(
columns = {
0: (level_1 + '_' + level_2)
}
)
return x_new