What is it?
BROADCASTCOPY is perfect for taking a measure and allocating it (“broadcasting”) to lower levels of the same dimension and/or additional dimensions. Typical uses include:
Taking a higher level input (e.g. Year level in an drivers table) and allocating it to lower levels (e.g. Months). Ideal for using high level drivers (e.g. annual pay increase) in detailed calculations (e.g. impact of pay increase on salary by month).
Taking a measure dimensionalized by Dimension1 and Dimension2 in a source table, and allocating it to Dimension3, Dimension 4, etc. in a target table. Ideal for taking high level drivers (e.g. regional growth rate %) and spreading across detailed workings (e.g. allocate growth rate % to all customers in that region).
How to write it?
Fx layout: = BROADCASTCOPY(Table.Measure,Dimension1)
Example = BROADCASTCOPY(Employee details.Start date,Time.Month)
Takes the employee’s start date from the Employee details table and allocates into all months in the receiving table. This date could then be used for determining new hire, total headcount and related costs for each month.
Knowledge Base link: https://www.arithmix.com/knowledge/measures-everyone-should-know