Daily DAX : Day 350 SAMPLE

Power BI DAX SAMPLE Function

Description

The SAMPLE function in Power BI DAX (Data Analysis Expressions) is used to retrieve a random sample of rows from a table. It is useful for statistical analysis, testing, or scenarios where you need a subset of data without bias.

Syntax

SAMPLE(<NumberOfRows>, <Table>, <OrderByExpression> [, <Order>] [, <OrderByExpression> [, <Order>]] ...)

• NumberOfRows: The number of rows to return (integer).
• Table: The table to sample from.
• OrderByExpression: (Optional) A column or expression to sort the table before sampling.
• Order: (Optional) ASC (ascending) or DESC (descending) for sorting. Default is ASC.

Return Value

A table containing a random subset of rows from the input table, with the specified number of rows.

Use Case

The SAMPLE function is commonly used in:

• Statistical Analysis: To analyze a representative subset of a large dataset.
• Testing: To work with a smaller, random sample of data during development or testing.
• Data Exploration: To quickly inspect a random subset of data without processing the entire table.

Example

Suppose you have a table Sales with columns Product, Region, and Revenue. You want to select a random sample of 5 rows, ordered by Revenue in descending order.

SampleSales = SAMPLE(5, Sales, Sales[Revenue], DESC)

This returns a table with 5 random rows from the Sales table, sorted by Revenue in descending order before sampling.

Notes

• The randomness is not guaranteed to be perfectly uniform, as it depends on the DAX engine's implementation.
• If NumberOfRows exceeds the table's row count, the entire table is returned.
• Use with caution in reports requiring consistent results, as the sample is random and may change on refresh.