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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 as (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**.