Removing the first rows before a specific value - pandas

Question

I am trying to remove all rows before an initial value for a group. For instance, if my max_value = 250, then all rows for a group before that value should be remov

Answer 1

This should do the trick:

df[df.groupby('Asset')['Monthly Value'].apply(lambda x: x.gt(max_value).cumsum().ne(0))]

Yields:

          date    Asset  Monthly Value
2   2019-03-01  Asset A            300
3   2019-04-01  Asset A            400
4   2019-01-01  Asset A            500
5   2019-02-01  Asset A            600
8   2019-01-01  Asset B            300
9   2019-02-01  Asset B            200
10  2019-03-01  Asset B            300
11  2019-04-01  Asset B            200

Additionally, if you store your max values in a dictionary like max_value = {'Asset A': 250, 'Asset B': 250}, you can do the following to achieve the same result:

df[df.groupby('Asset')['Monthly Value'].apply(lambda x: x.gt(max_value[x.name]).cumsum().ne(0))]