Pandas在groupby函数中计算空值

Pandas在groupby函数中计算空值

我认为你需要

groupby

使用

sum

的

NaN

值：

df2 = df.C.isnull().groupby([df['A'],df['B']]).sum().astype(int).reset_index(name='count')print (df2)     A      B  count0  bar    one      01  bar  three      02  bar    two      13  foo    one      24  foo  three      15  foo    two      2

如果需要过滤器，首先添加

boolean indexing

：

df = df[df['A'] == 'foo']df2 = df.C.isnull().groupby([df['A'],df['B']]).sum().astype(int)print (df2)A    B    foo  one      2     three    1     two      2

或更简单：

df = df[df['A'] == 'foo']df2 = df['B'].value_counts()print (df2)one      2two      2three    1Name: B, dtype: int64

编辑：解决方案非常相似，只添加

transform

：

df['D'] = df.C.isnull().groupby([df['A'],df['B']]).transform('sum').astype(int)print (df)     A      B     C  D0  foo    one   NaN  21  bar    one  bla2  02  foo    two   NaN  23  bar  three  bla3  04  foo    two   NaN  25  bar    two   NaN  16  foo    one   NaN  27  foo  three   NaN  1

类似的解决方案：

df['D'] = df.C.isnull()df['D'] = df.groupby(['A','B'])['D'].transform('sum').astype(int)print (df)     A      B     C  D0  foo    one   NaN  21  bar    one  bla2  02  foo    two   NaN  23  bar  three  bla3  04  foo    two   NaN  25  bar    two   NaN  16  foo    one   NaN  27  foo  three   NaN  1