Multiple Contexts in DAX

Define Multiple Contexts within Same Measure in DAX

Data Analysis Expressions (DAX) allows for multiple contexts within the same measure. The context in DAX combines two states: Row context and Filter context. It's perfectly permissible to use multiple contexts within the same DAX measure. The usage and combination of these contexts is what allows for detailed and dynamic calculations in Power BI.

Below is an example of a DAX function with multiple contexts:

MeasureName := 
CALCULATE (
    [ExistingMeasure],
    FILTER (
        'Table',
        'Table'[Column1] = "Value1"
            && 'Table'[Column2] > 5000
    ),
    ALL ('Table'[Column3])
)

In the above DAX expression:

• CALCULATE is used to modify the filter context of the calculation.

• FILTER is creating a new row context to iterate over the 'Table', and apply filters on 'Column1' and 'Column2'.

• ALL is clearing the filter context from 'Column3' (which can be thought of as another context since it impacts the calculation result).

So, this single measure is combining these multiple contexts to achieve the desired result.

Unit Testing

Unit testing is not direct and straightforward for DAX as compared to other programming languages. It requires building test environment in Power BI or Excel and then manually checking the results. It would involve creating a set of inputs and expected outputs, then manually checking if the measure returns the correct result.

Learning Resources

To learn more about contexts in DAX, you can check out the courses on Enterprise DNA platform. This platform includes comprehensive insight into filter context and row context, and how to use them effectively within DAX measures in Power BI.