In a Custom Data table you can create a column that produces a calculated value based on a formula defined in the setup of the column. Any number or measurement columns in the Data table can be incorporated in this formula.
To create a formula column:

Click the "add column" button in the Data table tool bar.

Select formula

Enter a name to be displayed as the column title.

Click "add column"

A modal will open to allow you to define the formula applied to each row in this column.
Building a formula
To build a formula, click on the blue chips to on the left hand side to select a number or measurement column to be incorporated (shown below in purple) as well as the components of the formula +  / * ( ) (shown below in grey). You can also type numbers into this formula (shown below in red).
When adding measurement columns to the formula play close attention to the dates under the column names to select the correct measurement.
Errors in a formula
You may see the following messages when building your formula:

Syntax error at character x

The formula is incomplete or an incompatible component has been entered.


At least one column must be selected

No columns have been selected from the list on the left. This formula is invalid.

These messages appear when the formula is either invalid or incomplete. Ensure you have built the formula by clicking on the blue chips and only typing numbers. All formulae must contain at least on column, added by clicking on a column name in the list on the left.
Note: Only the components in the the blue chips can be used in a formula, other components such as SUM(), AVERAGE() etc. are not supported in this calculation.
Editing a formula
After the column has been created, edit this formula by clicking on the arrowhead in the header to open the action menu and select Edit.