Rank categories with duplicate categories

Hi ruxandraalina 
I don't think there is a simple solution for this. The problem is that you want the count to increase by 1 everytime the group category changes which is not  a conventional requirement. However, this is a sample file with the solution https://www.dropbox.com/t/bf4kLtD0RgWQpoWh

This requires creating two calculated columns (it can be done with one column but would be too complex to implement)

Rank = 
VAR IncidentTable = 
    CALCULATETABLE ( Incidents, ALLEXCEPT ( Incidents, Incidents[IncidentNumber] ) )
VAR IncidentCategoryTable = 
    CALCULATETABLE ( Incidents, ALLEXCEPT ( Incidents, Incidents[IncidentNumber], Incidents[Group Category] ) )
VAR UniqueDateTime = 
    Incidents[StartDate] + Incidents[EndDate_custom]
VAR Rank1 = 
    RANKX ( IncidentTable, Incidents[StartDate] + Incidents[EndDate_custom],, ASC ) 
VAR Rank2 =
    RANKX ( IncidentCategoryTable, Incidents[StartDate] + Incidents[EndDate_custom],, ASC ) 
RETURN
    Rank1 - Rank2

Group Category  Rank = 
VAR IncidentTable =
    CALCULATETABLE ( Incidents, ALLEXCEPT ( Incidents, Incidents[IncidentNumber] ) )
VAR UniqueDate = Incidents[StartDate] + Incidents[EndDate_custom]
VAR PrevuiousTable =
    FILTER ( IncidentTable, Incidents[StartDate] + Incidents[EndDate_custom] <= UniqueDate )
VAR Ranks = 
    SELECTCOLUMNS ( PrevuiousTable, "@Rank", Incidents[Rank] )
RETURN
    COUNTROWS ( DISTINCT ( Ranks ) )