Cubic spline interpolation

We can interpolate missing data by using cubic spline in stata

first, install this package in stata:

ssc install csipolate

this is an example:

 Setup
        . webuse ipolxmpl1

    List the data
        . list, sep(0)

    Create y1 containing a natural cubic spline interpolation of y on
    x for missing values of y
        . csipolate y x, gen(y1)

    List the result
        . list, sep(0)