pandas 将多键值数据框列重塑为行

Question

我有一个像这样的数据框：

列(0 => 1, 2=> 3) 存储为记录如何重塑？ IE。列 metric_name 和 metric_value 和多行（观察）?

pandas_dict = {0: {0: 'Model:',
  1: 'Dependent Variable:',
  2: 'Date:',
  3: 'No. Observations:',
  4: 'Df Model:',
  5: 'Df Residuals:',
  6: 'Converged:',
  7: 'No. Iterations:'},
 1: {0: 'Logit',
  1: 'sick_percentage',
  2: '2019-08-14 13:32',
  3: '28',
  4: '2',
  5: '25',
  6: '0.0000',
  7: '35.0000'},
 2: {0: 'Pseudo R-squared:',
  1: 'AIC:',
  2: 'BIC:',
  3: 'Log-Likelihood:',
  4: 'LL-Null:',
  5: 'LLR p-value:',
  6: 'Scale:',
  7: ''},
 3: {0: 'inf',
  1: '6.0798',
  2: '10.0764',
  3: '-0.039902',
  4: '0.0000',
  5: '1.0000',
  6: '1.0000',
  7: ''}}
df = pd.DataFrame(pandas_dict)

Answer 1

如果只有 4 列，您可以展平值并通过构造函数创建 DataFrame：

a = df[[0, 2]].values.ravel()
b = df[[1, 3]].values.ravel()

df = pd.DataFrame({'A':a, 'B':b})
print (df)
                      A                 B
0                Model:             Logit
1     Pseudo R-squared:               inf
2   Dependent Variable:   sick_percentage
3                  AIC:            6.0798
4                 Date:  2019-08-14 13:32
5                  BIC:           10.0764
6     No. Observations:                28
7       Log-Likelihood:         -0.039902
8             Df Model:                 2
9              LL-Null:            0.0000
10        Df Residuals:                25
11         LLR p-value:            1.0000
12           Converged:            0.0000
13               Scale:            1.0000
14      No. Iterations:           35.0000
15

或通用解决方案 - 在具有模数和整数除法的列中创建 MultiIndex，并按 DataFrame.stack:

重塑

df.columns = [df.columns % 2, df.columns // 2]
df = df.stack().reset_index(drop=True)
print (df)
                      0                 1
0                Model:             Logit
1     Pseudo R-squared:               inf
2   Dependent Variable:   sick_percentage
3                  AIC:            6.0798
4                 Date:  2019-08-14 13:32
5                  BIC:           10.0764
6     No. Observations:                28
7       Log-Likelihood:         -0.039902
8             Df Model:                 2
9              LL-Null:            0.0000
10        Df Residuals:                25
11         LLR p-value:            1.0000
12           Converged:            0.0000
13               Scale:            1.0000
14      No. Iterations:           35.0000
15

Answer 2

如果您正在寻找更快的解决方案，也可以在此处使用 np.concatenate。

df=pd.DataFrame(np.concatenate( (df.iloc[:,[0,1]].values, df.iloc[:,[2,3]].values), axis=0 ),columns=['Metric Name','Metric Value'])

如果要使用pandas功能，可以使用

1) pandas.DataFrame.merge

df= df.iloc[:,[0,1]].rename(columns={0:'Metric Name',1:'Metric Value'}).merge(df.iloc[:,[2,3]].rename(columns={2:'Metric Name',3:'Metric Value'}),how='outer')

2) pandas.concat

df=pd.concat((df.iloc[:,[0,1]].rename(columns={0:'Metric Name',1:'Metric Value'}),df.iloc[:,[2,3]].rename(columns={2:'Metric Name',3:'Metric Value'})), ignore_index=True)

pandas 将多键值数据框列重塑为行

pandas reshape multi key value dataframe colums to rows

python

reshape

pandas