pandas 如何将熊猫数据框的两列相乘（行乘法）并将结果存储在新列中？
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How to multiply two columns of a pandas data-frame (row multiplication) and store the result in a new column?
提问by Czar.Wolfgang
Command
命令
df_main['Ranking'] = df_main['Porosity']*['Permeability']gives -
df_main['Ranking'] = df_main['Porosity']*['Permeability']给 -
TypeError: can't multiply sequence by non-int of type 'str'
类型错误：不能将序列乘以“str”类型的非整数
The attacehd picture (https://i.stack.imgur.com/0Asu3.png) has more information. My code snippet is at i.stack.imgur.com/ehqF5.png)
attacehd 图片（https://i.stack.imgur.com/0Asu3.png）有更多信息。我的代码片段位于 i.stack.imgur.com/ehqF5.png）
More info: https://i.stack.imgur.com/0Asu3.png
回答by Miriam Farber
First you need to convert the column type of the two columns to floats (otherwise you cannot multiply them). You can do that as follows:
首先需要将两列的列类型转换为浮点数（否则不能相乘）。你可以这样做：
df_main[['Porosity', 'Permeability']] = df_main[['Porosity', 'Permeability']].astype(float)
Then you can define the new column via multiplication:
然后您可以通过乘法定义新列：
df_main['Ranking'] = df_main['Porosity']*df_main['Permeability']
