Understanding the DAX CALCULATE function

Question

I am working on a model in Power BI that has two datasets:

Set_1 (just a list of each group name)

and Set_2, a bunch of values per group in a different dataset:

But I don't understand why the CALCULATE function, which doesn't take any filter contexts as parameters works the way it does in this instance

Answer 1

Using the CALCULATE function makes the DAX perform a context transition.

The value in the Group column of each row acts as a filter when you use CALCULATE as if you had written something like CALCULATE(SUM(Set_2[Value]), Set_2[Group] = 1). Even though it doesn't have an explicit filter, the row context acts as a filter.