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Configuring Expressions

Expressions are used when you need to perform calculations on your data or when you need to create more advanced aggregations in your visualizations.

Overview

When you add a calculated column, expressions are used to perform a calculation on an existing column. The calculated column is then added to the data table. Custom expressions are used on the axes of visualizations and create new aggregations for a visualization.

The syntax for the expressions and how they are created are the same for calculated columns and custom expressions, but the effect it has on your analysis differs.

Calculated Columns

As mentioned, a calculated column is added to your data table. The created column will, like other columns, be represented by a filter and can be used as any other column in your visualizations. This is useful if you want to add a new aspect to your data that can be calculated from the existing columns.

For example, a calculated column can be used to add a column with temperatures in Fahrenheit if you have a data table containing temperatures for different locations in Celsius. The expression then uses the values in the Celsius column to create a new column with calculated values representing the temperature in Fahrenheit.

Adding a calculated column

Custom Expressions

Custom expressions do not add a new column to your data table. Instead, they are used as aggregations on the axes of visualizations. They allow you to define your own, advanced aggregations, but essentially work the same way as the provided aggregations. The expressions are dynamic and are recalculated when filtering is performed on your data.

Right-clicking on an axis selector

For more information on expressions, see the following topics in the TIBCO Spotfire User's Guide: