I'm having week numbers in the dataframe from 1 to 52 e.g. [1,2,3,4,5,6,7,8,..52]
I'm trying to create a new column for month but it would mean an incremental assignment like [1,2,3,4] = 1, [5,6,7,8] = 2, .. [49,50,51,52] = 12
I tried getting the records by multiple of 4 using df[df["week"]%4==0] and then ffill it but seems like we can only assign it all to the same number which is not what I want. Instead I want to assign [1..12] accordingly. Is there another way to do this?
Subtract 1 first and then use integer division by 4:
df = pd.DataFrame({'week':range(1,53)})
df['new'] = (df["week"] - 1)//4
print (df.head(10))
week new
0 1 0
1 2 0
2 3 0
3 4 0
4 5 1
5 6 1
6 7 1
7 8 1
8 9 2
9 10 2
print (df.tail(10))
week new
42 43 10
43 44 10
44 45 11
45 46 11
46 47 11
47 48 11
48 49 12
49 50 12
50 51 12
51 52 12
If want starting by 1 it is possible, but last value is 13:
df['new'] = ((df["week"] - 1)//4) + 1
print (df.head(10))
week new
0 1 1
1 2 1
2 3 1
3 4 1
4 5 2
5 6 2
6 7 2
7 8 2
8 9 3
9 10 3
print (df.tail(10))
week new
42 43 11
43 44 11
44 45 12
45 46 12
46 47 12
47 48 12
48 49 13
49 50 13
50 51 13
51 52 13
If want values between 1 and 12 (but some groups has more like 4 values) use, solution by @Aryerez, thank you:
df['new'] = ((df["week"] - 1) // (52 / 12)).astype(int) + 1
print (df.head(10))
week new
0 1 1
1 2 1
2 3 1
3 4 1
4 5 1
5 6 2
6 7 2
7 8 2
8 9 2
9 10 3
print (df.tail(10))
week new
42 43 10
43 44 10
44 45 11
45 46 11
46 47 11
47 48 11
48 49 12
49 50 12
50 51 12
51 52 12
EDIT: For 5 values in each 3rd group use:
df['new'] = ((df["week"] + 4) // (52 / 12)).astype(int)
print (df.head(15))
week new
0 1 1
1 2 1
2 3 1
3 4 1
4 5 2
5 6 2
6 7 2
7 8 2
8 9 3
9 10 3
10 11 3
11 12 3
12 13 3
13 14 4
14 15 4
print (df.tail(15))
week new
37 38 9
38 39 9
39 40 10
40 41 10
41 42 10
42 43 10
43 44 11
44 45 11
45 46 11
46 47 11
47 48 12
48 49 12
49 50 12
50 51 12
51 52 12
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