Create New Column In Data Frame By Interpolating Other Column In Between A Particular Date Range - Pandas

I have a df as shown below. the data is like this. Date y 0 2020-06-14 127 1 2020-06-15 216 2 2020-06-16 4 3 2020-06-17 90 4 2020-06-18 82 5 2020-06-19

Solution 1:

With some tweaks to your function it works. np.where to create the new column, removing the = from your conditionals, and casting to int as per your expected output.

def df_interpolate(df, start_date, end_date): 
    df["Date"] = pd.to_datetime(df["Date"])
    df['y_new'] = np.where((df['Date'] > start_date) & (df['Date'] < end_date), np.nan, df['y'])
    df['y_new'] = df['y_new'].interpolate().round().astype(int)
    return df

         Date    y  y_new
0  2020-06-14  127    127
1  2020-06-15  216    216
2  2020-06-16    4      4
3  2020-06-17   90     90
4  2020-06-18   82     82
5  2020-06-19   70     74
6  2020-06-20   59     66
7  2020-06-21   48     58
8  2020-06-22   23     50
9  2020-06-23   25     42
10 2020-06-24   24     34
11 2020-06-25   22     26
12 2020-06-26   19     18
13 2020-06-27   10     10
14 2020-06-28   18     18
15 2020-06-29  157    157
16 2020-06-30   16     16
17 2020-07-01   14     14
18 2020-07-02  343    343