suggested below questions don’t sove my problem, because I want to add ordering based on rules. Suggested question don’t answer to that. And question is not a duplicate.
I have a DataFrame and I need to add a ‘new column’ with the order number of each value.
I was able to do that, but I wonder:
1- is there a more correct/elegant way to do this?
Also, is it possible:
2- to give equivalent numbers in the same order? For example in my case second and third rows have the same value, and is it possible to assign 2 for both of them?
3- to set rule for defining order for example, if difference between rows is less than 0,5 then they should be assigned the same row order. If more, then order number should increase.
Thank you in advance!
np.random.seed(42)
df2=pd.DataFrame(np.random.randint(1,10, 10), columns=['numbers'])
df2=df2.sort_values('numbers')
df2['ord']=1+np.arange(0, len(df2['numbers']))
>Solution :
If you want to use the same order number to identical "numbers", use groupby.ngroup:
df2['ord'] = df2.groupby('numbers').ngroup().add(1)
Output:
numbers ord
5 3 1
1 4 2
9 4 2
3 5 3
8 5 3
0 7 4
4 7 4
6 7 4
2 8 5
7 8 5
grouping with threshold
grouper = df2['numbers'].diff().gt(1).cumsum()
df2['ord_threshold'] = df2.groupby(grouper).ngroup().add(1)
Output:
numbers ord ord_threshold
5 3 1 1
1 4 2 1
9 4 2 1
3 5 3 1
8 5 3 1
0 7 4 2
4 7 4 2
6 7 4 2
2 8 5 2
7 8 5 2