What is the primary purpose of calculated columns in Power BI?

The primary purpose of calculated columns in Power BI is to create new data fields based on existing data. When you define a calculated column, you derive values from the data already present in your table using DAX (Data Analysis Expressions). This allows you to create new fields that can be used in your reports and analytics, enhancing your data model by adding further insights without altering the underlying data source.

For example, you might create a calculated column that concatenates first and last names to provide a full name or that categorizes numerical values into ranges (like grouping sales into 'low', 'medium', or 'high'). The flexibility of calculated columns allows users to enrich their datasets and create more informative visualizations.

In contrast to other choices, combining data from multiple tables typically involves creating relationships or using measures rather than calculated columns. The notion of performing on-the-fly data analysis usually pertains to using measures or visualizations dynamically based on user input or filters applied in real-time. Visualization of data in graphs is purely about how the data is displayed, relying on existing data or calculated measures rather than creating new fields. Thus, calculated columns specifically focus on enriching and enhancing the dataset itself.