Marco Russo and Alberto Ferrari explain the idea of context transition in DAX:
Let us state this from the very beginning: context transition is a simple concept. It is a powerful feature aiming to simplify the authoring of DAX code. That said, most new DAX developers find context transition hard to understand, and they consider it to be the major reason behind incorrect results. There are two reasons for developers to feel this way:
– A solid understanding of the difference between the row context and the filter context is an important prerequisite to understand and master the concept of context transition.
– You need to remember when and how the context transition works. Most errors involving context transition are due to the developer forgetting to take the context transition into account, rather than not knowing how it works. Once they realize that context transition is happening, the code suddenly makes sense.
Read on to understand more about the idea of context transition.