python - 列变化计数器

Question

当第三列发生变化时，我将如何在列中创建两个计数器？例如，我有下面的Flag，我想从一列开始计数，然后当Flag改变时将其值更改为nan，并在另一列中计数，以这种方式继续来回计数。

Flag    Counter1    Counter2
   0           1         nan
   0           1         nan
   0           1         nan
   1         nan           1
   1         nan           1
   1         nan           1
   0           2         nan
   1         nan           2

Answer 1

您可以使用:

#create consecutives groups
a = df['Flag'].ne(df['Flag'].shift()).cumsum()

m1 = df['Flag'] == 1
m2 = df['Flag'] == 0
#get Trues for edge rows
m3 = ~a.duplicated()

m4 = m3 & m1
m5 = m3 & m2

#add NaNs or count by cumulative sum
df['Counter2'] =  np.where(m2, np.nan, m4.cumsum())
df['Counter1'] =  np.where(m1, np.nan, m5.cumsum())
print (df)
   Flag  Counter1  Counter2
0     0       1.0       NaN
1     0       1.0       NaN
2     0       1.0       NaN
3     1       NaN       1.0
4     1       NaN       1.0
5     1       NaN       1.0
6     0       2.0       NaN
7     1       NaN       2.0