Pandas ValueError:Grouper for'；C'；非一维

使用此数据帧

df = pd.DataFrame({"A": ["foo", "foo", "foo", "foo", "foo",
                         "bar", "bar", "bar", "bar"],
                   "B": ["one", "one", "one", "two", "two",
                         "one", "one", "two", "two"],
                   "C": ["small", "large", "large", "small",
                         "small", "large", "small", "small",
                         "large"],
                   "D": [1, 2, 2, 3, 3, 4, 5, 6, 7],
                   "E": [2, 4, 5, 5, 6, 6, 8, 9, 9]})
'''
     A    B      C  D  E
0  foo  one  small  1  2
1  foo  one  large  2  4
2  foo  one  large  2  5
3  foo  two  small  3  5
4  foo  two  small  3  6
5  bar  one  large  4  6
6  bar  one  small  5  8
7  bar  two  small  6  9
8  bar  two  large  7  9
'''

当我跑的时候

print(pd.pivot_table(df, values='C', index=['A', 'B'],
                    columns=['C'], aggfunc='count'))

根据A列和B列计算小/大的数量（例如，对于

A，B=（foo，one）

我们在C列中有1个

small

，2个

large

）

这给了我错误

ValueError: Grouper for 'C' not 1-dimensional

---

问题是什么？如何解决？

听起来你想要的实际上是一个groupby：

df.groupby(['A', 'B', 'C']).size()

A    B    C    
bar  one  large    1
          small    1
     two  large    1
          small    1
foo  one  large    2
          small    1
     two  small    2
dtype: int64

如果要将“C”放回列中，可以取消堆叠：

df.groupby(['A', 'B', 'C']).size().unstack().fillna(0)

C        large  small
A   B                
bar one    1.0    1.0
    two    1.0    1.0
foo one    2.0    1.0
    two    0.0    2.0

---

听起来你想要的其实是一个团员：

df.groupby(['A', 'B', 'C']).size()

A    B    C    
bar  one  large    1
          small    1
     two  large    1
          small    1
foo  one  large    2
          small    1
     two  small    2
dtype: int64

如果要将“C”放回列中，可以取消堆叠：

df.groupby(['A', 'B', 'C']).size().unstack().fillna(0)

C        large  small
A   B                
bar one    1.0    1.0
    two    1.0    1.0
foo one    2.0    1.0
    two    0.0    2.0

不能将C列同时作为值和列。 可能您应该改为：

print(pd.pivot_table(df, index=['A', 'B'], columns=['C'], aggfunc='count'))

结果是：

            D           E      
C       large small large small
A   B                          
bar one   1.0   1.0   1.0   1.0
    two   1.0   1.0   1.0   1.0
foo one   2.0   1.0   2.0   1.0
    two   NaN   2.0   NaN   2.0

不能将C列同时作为值和列。 可能您应该改为：

print(pd.pivot_table(df, index=['A', 'B'], columns=['C'], aggfunc='count'))

结果是：

            D           E      
C       large small large small
A   B                          
bar one   1.0   1.0   1.0   1.0
    two   1.0   1.0   1.0   1.0
foo one   2.0   1.0   2.0   1.0
    two   NaN   2.0   NaN   2.0