Question

使用pandas数据框，并尝试在分组输出中将其翻转，该输出采用唯一值并将其作为一列，并将每个值的对应计数作为新数据框中的值。

这是起始数据帧：

df = pd.DataFrame([('gold', 'bronze', 'silver'),
                   ('silver', 'gold', 'bronze'),
                   ('gold', 'silver', 'bronze'),
                   ('bronze', 'silver', 'gold')],
                    columns=('Canada', 'China', 'South Korea'))
df.head()

    Canada  China   South Korea
0   gold    bronze  silver
1   silver  gold    bronze
2   gold    silver  bronze
3   bronze  silver  gold

所需的输出将是这样的：

    nation      gold    silver  bronze
0   Canada        2          1       1
1   China         1          2       1
2   South Korea   1          1       2

Answer 1

您可以将df.apply与pd.value_counts ^*

一起使用

df.apply(pd.value_counts).T

             bronze  gold  silver
Canada            1     2       1
China             1     1       2
South Korea       2     1       1

^{*我找不到pd.value_counts的文档，因此将github链接链接到该函数。}

^{编辑：在读取源代码pd.Series.value_counts时，仅调用pd.value_counts}

Answer 2

使用pd.get_dummies和sum

pd.get_dummies(df.T, prefix='',prefix_sep='').sum(level=0,axis=1)

Out[995]:
             bronze  gold  silver
Canada            1     2       1
China             1     1       2
South Korea       2     1       1

Answer 3

w = df.melt()

    variable    value
0   Canada      gold
1   Canada      silver
2   Canada      gold
3   Canada      bronze
4   China       bronze
5   China       gold
6   China       silver
7   China       silver
8   South Korea silver
9   South Korea bronze
10  South Korea bronze
11  South Korea gold

然后：

pd.crosstab(w['variable'],w['value'])

所需结果：

value        bronze gold    silver
variable            
Canada        1      2       1
China         1      1       2
South Korea   2      1       1

Answer 4

df = pd.DataFrame([('gold', 'bronze', 'silver'),
               ('silver', 'gold', 'bronze'),
               ('gold', 'silver', 'bronze'),
               ('bronze', 'silver', 'gold')],
                columns=('Canada', 'China', 'South Korea')).transpose()

df.apply(pd.value_counts,axis=1)

熊猫唯一值作为带有计数的列

4 个答案: