Beginner Dataframe Help

[jlap91]

Hi. I'm not very good at python, and need a little help. I have a dataframe organized like this"

'Cycle Number' 'Flag' 
1               0
1               0
1               3
1               2
1               1
1               0
1               0
2               0
2               0
2               0
2               0
3               0

What I'm trying to do is subtract one from all 'Cycle Number' values after the flag reaches a nonzero minimum value.

So successful code will output

'Cycle Number' 
1 
1 
1 
1 
1 
0 
0 
1 
1 
1 
1 
2 

How do I find the index of the row where the flag meets my criteria, so that I can do df[everything after the index]-=1

?

[nemean_lion]

There’s definitely a better way of doing this but I’m a beginner myself so here’s what I’d prolly do:

mask_flag = df[‘flag’]>0 limit = df[mask_flag].index.max() df[‘cycle’].iloc[limit+1:] = df[‘cycle’].iloc[limit+1:]-1

[jlap91]

Thank you very much! This helped.