Count all occurrences of reference, ignoring visual and dividing equally

Question

I've come across another fuzzy scenario and I'm wondering if anyone may be able to help.

I have three tables

Invoices

Invoice Ref	Value
Inv1	10,000
Inv2	9,999

Invoice Categories

Invoice Ref	Category
Inv1	1
Inv2	2
Inv2	2

Categories

Category Ref	Description
1	Stuff
2	Things

They join to create a situation where an invoice can have multiple categories.

I have a PowerBI visual that displays like this

Invoice Ref	Count	Value	Category
Inv1	1	10,000	Stuff
Inv1	1	10,000	Things
Inv2	1	9,999	Things

However, I need it to be (counting the total rows of the reference and dividing equally between the two)

Invoice Ref	Count	Value	Category
Inv1	2	5,000	Stuff
Inv1	2	5,000	Things
Inv2	1	9,999	Things

Sorry for the table spam. I can't find a decent way to articulate it. Also, what is this operation called so I can do some reading?

Answer 1

This feels wrong or dirty - anyways try the following Measures:

Category count = 
  var meCount = COUNTROWS('Invoice Categories')
  var allCount = 
    CALCULATE(
      COUNTROWS('Invoice Categories'),
      ALLSELECTED('Categories')
    )
  return IF(NOT ISBLANK(meCount), allCount)


Invoice Category amount = 
  var s = SUM(Invoices[Value])
  return
    IF(
      ISINSCOPE('Categories'[Description]),
      DIVIDE(s, [Category count]),
      s
    )