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Python Pandas For Your Grandpa - 5.2 Challenge: Pickle

2021-02-01 346 words 2 minutes

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Setup

Given a Series called pickle, replace NaNs using the following algorithm.

For each NaN:

get the nearest non-NaN value before and after it
replace NaN with the minimum of those two non-NaN values

For NaNs on or near the endpoints of the Series, use the closest non-NaN value.

import numpy as np
import pandas as pd

pickle = pd.Series([1.5, np.nan, 2.3, np.nan, np.nan, -3.9, np.nan, 4.5, np.nan, np.nan, np.nan, 1.9, np.nan])
print(pickle)
## 0     1.5
## 1     NaN
## 2     2.3
## 3     NaN
## 4     NaN
## 5    -3.9
## 6     NaN
## 7     4.5
## 8     NaN
## 9     NaN
## 10    NaN
## 11    1.9
## 12    NaN
## dtype: float64

Solution

prevs = pickle.ffill()
nexts = pickle.bfill()
pickle.fillna(pd.concat([prevs, nexts], axis=1).min(axis=1))
## 0     1.5
## 1     1.5
## 2     2.3
## 3    -3.9
## 4    -3.9
## 5    -3.9
## 6    -3.9
## 7     4.5
## 8     1.9
## 9     1.9
## 10    1.9
## 11    1.9
## 12    1.9
## dtype: float64

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