Python：如何从数据框中查找数据并根据列匹配在另一个数据框中相乘

Question

我有一个数据框 df1，它具有以下结构

A   B   C   D
10  9   9   4
5   4   4   9
5   10  6   4
9   9   9   4
4   7   10  7
9   7   4   8
5   7   8   9
10  4   10  6

我有另一个数据帧 df2 如下，

name    factor
A   2
B   3
C   4
D   8

如何从 df2 中查找 A、B、C、D 的值并与 df1 [A、B、C、D] 相乘并得到 df3，例如，

A   B   C   D
20  27  36  32
10  12  16  72
10  30  24  32
18  27  36  32
8   21  40  56
18  21  16  64
10  21  32  72
20  12  40  48

Answer 1

使用mul for multiple by Series created by set_index:

df3 = df1.mul(df2.set_index('name')['factor'])
print (df3)
    A   B   C   D
0  20  27  36  32
1  10  12  16  72
2  10  30  24  32
3  18  27  36  32
4   8  21  40  56
5  18  21  16  64
6  10  21  32  72
7  20  12  40  48

详情：

print (df2.set_index('name')['factor'])
name
A    2
B    3
C    4
D    8
Name: factor, dtype: int64

编辑：

如果缺少某些类别，可以使用 fillna，谢谢 :

s = df2.set_index('name').drop('D')['factor']
print (s)
name
A    2
B    3
C    4
Name: factor, dtype: int64

df3 = df1.mul(s).fillna(df1)
print (df3)
      A     B     C    D
0  20.0  27.0  36.0  4.0
1  10.0  12.0  16.0  9.0
2  10.0  30.0  24.0  4.0
3  18.0  27.0  36.0  4.0
4   8.0  21.0  40.0  7.0
5  18.0  21.0  16.0  8.0
6  10.0  21.0  32.0  9.0
7  20.0  12.0  40.0  6.0

编辑 1：

如果要比较 DataFrame 和 Series:

s = df2.set_index('name')['factor']
print (s)
name
A    2
B    3
C    4
D    8
Name: factor, dtype: int64

df1['A'] = (np.log(df1['A']) * s['A']) ** 3
print (df1)
           A   B   C  D
0  97.664572   9   9  4
1  33.351293   4   4  9
2  33.351293  10   6  4
3  84.862013   9   9  4
4  21.313578   7  10  7
5  84.862013   7   4  8
6  33.351293   7   8  9
7  97.664572   4  10  6

对于所有列：

df1 = (np.log(df1) * s) ** 3
print (df1)
           A           B           C            D
0  97.664572  286.409295  678.896108  1364.068975
1  33.351293   71.933325  170.508622  5431.168861
2  33.351293  329.617932  368.145163  1364.068975
3  84.862013  286.409295  678.896108  1364.068975
4  21.313578  198.944581  781.316579  3772.578718
5  84.862013  198.944581  170.508622  4603.732789
6  33.351293  198.944581  575.466599  5431.168861
7  97.664572   71.933325  781.316579  2945.161306

Python：如何从数据框中查找数据并根据列匹配在另一个数据框中相乘

Python: How to row look up data from a dataframe and multiply in another dataframe based on columns match

python

lookup

numpy

dataframe

pandas