What Are Aggregation Functions?

Aggregation functions are used to perform calculations on a set of values to return a single summary value. These functions aggregate data points by grouping them based on certain criteria and then applying a mathematical operation to each group.

Common Aggregation Functions in Tableau:

1. SUM()
   • Definition: Adds all values in a specified field.
   • Use Case: Calculating total sales or total expenses over a period.
2. AVG()
   • Definition: Calculates the average value of a specified field.
   • Use Case: Determining the average sales per day or the average customer rating.
3. COUNT()
   • Definition: Counts the number of items in a specified field.
   • Use Case: Counting the number of transactions or the number of unique customers.
4. MAX()
   • Definition: Finds the maximum value in a specified field.
   • Use Case: Identifying the highest sales amount or the maximum temperature recorded.
5. MIN()
   • Definition: Finds the minimum value in a specified field.
   • Use Case: Determining the lowest sales figure or the minimum stock level.
6. MEDIAN()
   • Definition: Returns the median value of a specified field.
   • Use Case: Finding the median salary or the median product rating.
7. STDEV()
   • Definition: Calculates the standard deviation of a specified field, which measures the amount of variation or dispersion.
   • Use Case: Analyzing the variability in sales performance or customer satisfaction scores.
8. PERCENTILE()
   • Definition: Returns the value below which a given percentage of observations fall.
   • Use Case: Assessing the 90th percentile of sales figures or the 25th percentile of customer ratings.

How Aggregation Functions Work

Aggregation functions are applied to measures in Tableau to summarize data based on dimensions in the view. For example, when analyzing sales data, you might use SUM() to calculate the total sales per region, AVG() to find the average sales per month, and COUNT() to determine the number of transactions.

Key Points to Remember:

• Aggregation functions are applied to measures and depend on the context of dimensions in the view.
• Aggregations can be adjusted by changing the level of detail or adding filters to refine the data being summarized.

Example: To find the total sales for each product category, you would use the SUM() function on the sales measure, grouped by the product category dimension.