How can i remove consecutive pairs of equal numbers with opposite signs from a Pandas dataframe?

Assuming i have this input dataframe

incremental_changes = [2, -2, 2, 1, 4, 5, -5, 7, -6, 6]
df = pd.DataFrame({
    'idx': range(len(incremental_changes)),
    'incremental_changes': incremental_changes
})

   idx  incremental_changes
0    0                    2
1    1                   -2
2    2                    2
3    3                    1
4    4                    4
5    5                    5
6    6                   -5
7    7                    7
8    8                   -6
9    9                    6

I would like to get the following

   idx  incremental_changes
0    0                    2
3    3                    1
4    4                    4
7    7                    7

Note that the first 2 could either be idx 0 or 2, it doesn't really matter.

Thanks

CodePudding user response：

Can groupby consecutive equal numbers and transform

import itertools

def remove_duplicates(s):
    ''' Generates booleans that indicate when a pair of ints with
        opposite signs are found.
    '''
    iter_ = iter(s)
    for (a,b) in itertools.zip_longest(iter_, iter_):
        if b is None:
            yield False
        else:
            yield a b == 0
            yield a b == 0

>>> mask = df.groupby(df['incremental_changes'].abs().diff().ne(0).cumsum()) \
             ['incremental_changes'] \
             .transform(remove_duplicates)

Then

>>> df[~mask]

   idx  incremental_changes
2    2                    2
3    3                    1
4    4                    4
7    7                    7

CodePudding user response：

Just do rolling, then we filter the multiple combine

s = df.incremental_changes.rolling(2).sum()
s = s.mask(s[s==0].groupby(s.ne(0).cumsum()).cumcount()==1)==0
df[~(s | s.shift(-1))]
Out[640]: 
   idx  incremental_changes
2    2                    2
3    3                    1
4    4                    4
7    7                    7