DAX Function: Sum with Input Validation

Overview

This function sums a specified column from a given table, allowing optional filtering. It includes robust input validation and comprehensive documentation.

Function Definition

Below is the DAX code for the SumColumn function.

DAX Code

SumColumn = 
VAR TableName = "YourTableName"  // Replace with your table name
VAR ColumnName = "YourColumnName"  // Replace with your column name
VAR FilterExpression = [YourFilterExpression]  // Replace with optional filter logic

RETURN 
    // Check if the table and column exist
    IF (
        HASONEVALUE(TableName[ColumnName]), 
        SUMX (
            FILTER (
                TableName, 
                FilterExpression
            ), 
            TableName[ColumnName]  // Sum specified column
        ),
        BLANK()  // Return blank if invalid input
    )

Parameters

• TableName: The name of the table containing the column to sum.
• ColumnName: The name of the column to sum.
• FilterExpression: An optional expression to filter the rows.

Return Type

• Returns the sum of the specified column as a numeric value, or BLANK() if the input is invalid.

Input Validation

• Table Existence Check: Ensures the specified table and column exist.
• Filter Logic: Validates that the filter expression returns valid data.

Commentary

• The function uses VAR to define table and column references for better readability.
• It utilizes HASONEVALUE to validate whether a single column value is passed for calculations.
• FILTER is used effectively to apply any filtering condition before summation.

Code Usage Example

Assuming you have a sales table called Sales with a column named Amount and you want to filter where the region is "North", you can use it as follows:

TotalSalesNorth = 
SumColumn(Sales, Amount, Sales[Region] = "North")

• TotalSalesNorth will provide the sum of the Amount column from the Sales table only for the "North" region.

Conclusion

This DAX function offers a structured approach to summing values with optional filtering, making it a useful asset for data analytics within Power BI.

For further learning, consider exploring courses on the Enterprise DNA Platform, which covers advanced DAX techniques and best practices.