This script will fill missing values within a column based on other occurrences of data:
In this illustrative data table, we might choose to forward-fill the Jan Ozone column or back-fill the Dec Ozone column.
For example, forward-filling the Jan Ozone column would set the value of 2.63 for the whole of 1955; back-filling the Dec Ozone column would set the value to 3.83 for the whole of 1955.
This type of data often arises when two tables are joined, but they have differing sample rates.
The script allows you to specify the direction of the fill, and whether to fill in-place or to create a new column: