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

 The WINDOW_STDEV() function in Tableau is a table calculation function that calculates the sample standard deviation of a given field or expression over a specified window or range of values. It measures the dispersion or spread of data points around their mean within the window.

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

WINDOW_STDEV(expression, [start, end])

• expression: The field or calculation for which you want to calculate the standard deviation.
• 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_STDEV() function in Tableau:

Suppose you have a dataset that contains information about the monthly sales of different products. You want to calculate the sample standard deviation of the sales values over a rolling three-month window.

1. Open Tableau and connect to your dataset.
2. Create a view that includes the "Date" field and the "Sales" field.
3. Right-click on the "Sales" field and select "Add Table Calculation."
4. In the calculation dialog box, choose "STDEV" from the list of table calculation functions.
5. Specify the expression as the field or calculation for which you want to calculate the standard deviation (in this case, "Sales").
6. Configure the specific settings for the WINDOW_STDEV function, such as the addressing and partitioning options, to define the three-month rolling window.
7. Click "OK" to apply the WINDOW_STDEV function to the sales values.

Tableau will calculate the sample standard deviation of the sales values over the specified rolling three-month window. The standard deviation measures the dispersion of values around the mean, indicating the variability or spread of the sales values within the window.

You can further customize the view, apply sorting, or add additional calculations based on the calculated standard deviation. For example, you can create a visualization that shows the trend of the standard deviation over time or compare the standard deviations across different products.

The WINDOW_STDEV function allows you to perform calculations related to the sample standard deviation within a specified window. It helps you understand the variability and dispersion of values within a dataset and supports data analysis and visualization based on these measures.