Explain the Table Calculation Function 'WINDOW_SUM() in Tableau with Example?

The WINDOW_SUM() function in Tableau is a table calculation function that calculates the sum of a given field or expression over a specified window or range of values. It allows you to perform calculations on a set of rows within the view, defined by the addressing and partitioning options.

The syntax for the WINDOW_SUM() function in Tableau is as follows:

WINDOW_SUM(expression, [start, end])

• expression: The field or calculation for which you want to calculate the sum.
• start (optional): The starting point of the window. If not specified, the window starts from the first data point.
• end (optional): The ending point of the window. If not specified, the window ends at the current data point.

Here's an example to demonstrate how to use the WINDOW_SUM() function in Tableau:

Suppose you have a dataset that contains information about the monthly sales of different products. You want to calculate the cumulative sum of the sales values over time.

1. Open Tableau and connect to your dataset.
2. Create a view that includes the "Date" field and the "Sales" field.
3. Drag the "Sales" field to the Marks card to apply the aggregation.
4. Right-click on the "Sales" field and select "Add Table Calculation."
5. In the calculation dialog box, choose "SUM" from the list of table calculation functions.
6. Specify the expression as the field or calculation for which you want to calculate the sum (in this case, "Sales").
7. Configure the specific settings for the WINDOW_SUM function, such as the addressing and partitioning options, to define the desired window (e.g., using the "Table Across" option to calculate the cumulative sum over time).
8. Click "OK" to apply the WINDOW_SUM function to the sales values.

Tableau will calculate the cumulative sum of the sales values over time based on the applied table calculation. The cumulative sum represents the running total of the sales values up to the current point in the view.

You can further customize the view, apply sorting, or add additional calculations based on the cumulative sum. For example, you can create a line chart that shows the trend of the cumulative sales over time or compare the cumulative sums across different products.

The WINDOW_SUM function allows you to perform calculations related to the sum within a specified window. It helps you understand the cumulative or running total of values within a dataset and supports various data analysis and visualization scenarios.

I hope this explanation clarifies the usage of the WINDOW_SUM() function in Tableau.