MultiIndex 在使用 pd.concat 时的名称消失

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英文:

MultiIndex names when using pd.concat disappeared

问题

考虑到你的要求，以下是翻译好的部分：

  1. 考虑以下数据框 `df1` 和 `df2`：
  3.     df1: 
  4.     sim_names       Model 1          
  5.     signal_names     my_y1     my_y2
  6.     units               °C       kPa
  7.     (Time, s)                       
  8.     0.0           0.738280  1.478617
  9.     0.1           1.078653  0.486527
  10.     0.2           0.794123  0.604792
  11.     0.3           0.392690  1.072772 
  12.     
  13.     df2: 
  14.      空的数据框
  15.     列: []
  16.     索引: [0.0, 0.1, 0.2, 0.3] 
  18. 正如你所见，`df1` 有三个级别的名称分别为 `"sim_names"`、`"signal_names"` 和 `"units"`。
  20. 接下来，我想要将这两个数据框连接起来，因此我运行了以下命令：
  22.         df2 = pd.concat(
  23.             [df1, df2],
  24.             axis="columns",
  25.         )
  27. 但是我得到了以下结果：
  29.      df2:
  30.                  Model 1          
  31.                   my_y1     my_y2
  32.                      °C       kPa
  33.     (Time, s)                    
  34.     0.0        0.738280  1.478617
  35.     0.1        1.078653  0.486527
  36.     0.2        0.794123  0.604792
  37.     0.3        0.392690  1.072772 
  39. 正如你所见，级别名称消失了。
  41. 我应该怎么做才能在结果的 `df2` 中保留 `df1` 的级别名称？
  43. 我想要的结果 `df2` 应该像下面这样：
  45.     df2: 
  46.     sim_names       Model 1          
  47.     signal_names     my_y1     my_y2
  48.     units               °C       kPa
  49.     (Time, s)                       
  50.     0.0           0.738280  1.478617
  51.     0.1           1.078653  0.486527
  52.     0.2           0.794123  0.604792
  53.     0.3           0.392690  1.072772 
  55. 我尝试将 `names=["sim_names", "signal_names", "units"]` 作为参数传递给 `pd.concat`，但是得到了与上述相同的错误结果。
英文:

Consider the following dataframes df1 and df2:

  1. df1: 
  2. sim_names       Model 1          
  3. signal_names     my_y1     my_y2
  4. units               °C       kPa
  5. (Time, s)                       
  6. 0.0           0.738280  1.478617
  7. 0.1           1.078653  0.486527
  8. 0.2           0.794123  0.604792
  9. 0.3           0.392690  1.072772 
  11. df2: 
  12.  Empty DataFrame
  13. Columns: []
  14. Index: [0.0, 0.1, 0.2, 0.3]

As you see, df1 has three levels with names "sim_names", "signal_names" and "units".

Next, I want to concatenate the two dataframes, and therefore I run the following command:

  1.     df2 = pd.concat(
  2.         [df1, df2],
  3.         axis="columns",
  4.     )

but what I get is the following:

  1.  df2:
  2.              Model 1          
  3.               my_y1     my_y2
  4.                  °C       kPa
  5. (Time, s)                    
  6. 0.0        0.738280  1.478617
  7. 0.1        1.078653  0.486527
  8. 0.2        0.794123  0.604792
  9. 0.3        0.392690  1.072772

As you see, the levels names are gone.

What should I do to keep the levels names of df1 in the resulting df2?

My wanted resulting df2 should be like the following:

  1. df2: 
  2. sim_names       Model 1          
  3. signal_names     my_y1     my_y2
  4. units               °C       kPa
  5. (Time, s)                       
  6. 0.0           0.738280  1.478617
  7. 0.1           1.078653  0.486527
  8. 0.2           0.794123  0.604792
  9. 0.3           0.392690  1.072772

I tried to pass names=["sim_names", "signal_names", "units"] as argument to pd.concat but I got the same wrong result as above.

答案1

得分: 1

I'm not sure but seems like this is the normal behaviour (see GH13475).

作为一种解决方法，您可以使用 rename_axis/names :

  1. out = pd.concat(
  2.         [df1, df2],
  3.         axis="columns",
  4.     ).rename_axis(df1.columns.names, axis=1) # <- added chain

​
Output :

  1. print(out)
  3. sim_names    Model 1      
  4. signal_names   my_y1 my_y2
  5. units             ℃   kPa
  6. (Time, s)                 
  7. 0.00            0.74  1.48
  8. 0.10            1.08  0.49
  9. 0.20            0.79  0.60
  10. 0.30            0.39  1.07
英文:

I'm not sure but seems like this is the normal behaviour (see GH13475).

As a workaround, you can use rename_axis/names :

  1. out = pd.concat(
  2.         [df1, df2],
  3.         axis=&quot;columns&quot;,
  4.     ).rename_axis(df1.columns.names, axis=1) # &lt;- added chain

​
Output :

  1. print(out)
  3. sim_names    Model 1      
  4. signal_names   my_y1 my_y2
  5. units             &#176;C   kPa
  6. (Time, s)                 
  7. 0.00            0.74  1.48
  8. 0.10            1.08  0.49
  9. 0.20            0.79  0.60
  10. 0.30            0.39  1.07

huangapple
  • 本文由 发表于 2023年5月11日 03:16:27
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  • dataframe
  • pandas
  • python
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