Say only one analyst is visible in the current context. Then, the calculation would be:
-- measure you need first
[# Closed Cases] =
-- 'Calendar' must join to the FactTable on a Date field
-- (the other field is [Date Of Closure]
-- and be designated as Date Table in the model. Please make
-- sure you follow the rules of creating a proper Calendar.
-- Without a good calendar a model is almost worthless and
-- prone to errors.
[Analyst Average] :=
var __onlyOneAnalystVisible = HASONEFILTER( FactTable[Analyst Name] )
var __minNumOfCases = 2
var __numOfWorkedDays =
[# Closed Cases] >= __minNumOfCases
var _totalNumOfCases = [# Closed Cases]
DIVIDE( __totalNumOfCases, __numOfWorkedDays )
If you'd like to adjust it for a set of analysts, then you'd have to define the logic of what you mean by a daily average for a set of analysts.