根据另一列的值增加列值

Question

I have a df as below:

       ID  Value  counter  
    0  A   30      3
    1  A   30      3
    2  A   30      3
    3  A   30      3
    4  A   30      3
    5  A   30      3
    6  B   50       2
    7  B   50       2
    8  B   50       2
    9  B   50       2
   10  C   40      2
   11  C   40      2
   12  C   40      2
   13  C   40      2

I want to add a new column Value1 . At every repetition of ID the value in column Value should be incremented and saved in column Value1 . However, it should only be incremented by number given in column Counter then it should repeat. Below is the desired output.

   ID  Value  counter  Value1
0  A   30      3        31
1  A   30      3        32
2  A   30      3        33
3  A   30      3        31
4  A   30      3        32
5  A   30      3        33 
6  B   50      2        51
7  B   50      2        52
8  B   50      2        51
9  B   50      2        52
10  C   40      2        41
11  C   40      2        42
12  C   40      2        41
13  C   40      2        42

My attempt:

df['Value1'] = df['Value']
df['Value1'] += df.groupby('ID')['Value1'].cumcount() +1

But this does not consider the counter and just increments. How is it possible to repeat the increment after the counter value has reached.

Answer 1

You'll need to use the modulo operator to reset your .cumcount by the value of df["counter"]

df["Value1"] = (
    df["Value"] + df.groupby("ID")["Value"].cumcount().mod(df["counter"]).add(1)
)

print(df)
   ID  Value  counter  Value1
0   A     30        3      31
1   A     30        3      32
2   A     30        3      33
3   A     30        3      31
4   A     30        3      32
5   A     30        3      33
6   B     50        2      51
7   B     50        2      52
8   B     50        2      51
9   B     50        2      52
10  C     40        2      41
11  C     40        2      42
12  C     40        2      41
13  C     40        2      42