CODEWITHSUNDEEP
pythonpandasinterpolation
Mips
Mips

Reputation: 151

Why does pandas.interpolate() interpolate single values surrounded by NaNs?

I have a problem with pandas interpolate(). I only want to interpolate when there are not more than 2 succsessive "np.nans". But the interpolate function tries to interpolate also single values when there are more than 2 np.nans!?

s = pd.Series(data = [np.nan,10,np.nan,np.nan,np.nan,5,np.nan,6,np.nan,np.nan,30])
a = s.interpolate(limit=2,limit_area='inside')
print(a)

the output I get is:

0       NaN
1     10.00
2      8.75
3      7.50
4       NaN
5      5.00
6      5.50
7      6.00
8     14.00
9     22.00
10    30.00
dtype: float64

I do not want the result in line 2 and 3. What I want is:

0       NaN
1     10.00
2       NaN
3       NaN
4       NaN
5      5.00
6      5.50
7      6.00
8     14.00
9     22.00
10    30.00
dtype: float64

Can anybody please help?

Upvotes: 1

Views: 191

Answers (1)

ansev
ansev

Reputation: 30920

Groupby.transform with Series.where

s_notna = s.notna()
m = (s.groupby(s_notna.cumsum()).transform('size').le(3) | s_notna)    
s = s.interpolate(limit_are='inside').where(m)
print(s)

Output

0      NaN
1     10.0
2      NaN
3      NaN
4      NaN
5      5.0
6      5.5
7      6.0
8     14.0
9     22.0
10    30.0
dtype: float64

Upvotes: 1

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