Return Date based on Conditions from same table

[bron12321]

Hi, i've been trying to follow this: Solved: Date difference between values in same column - Microsoft Fabric Community

Since I want to get a similar result. I need to calculate the difference in days from the BaselineDate to Forecast Date for each unique ID to determine if items are running on schedule (The dataset is incomplete - not all IDs have dates set) . I have the following [Master] table: 

with the calculated column:

DiffBaselineForcast_days =

VAR _ID = Master[UniqueID]

VAR temp =

    TOPN (

        1,

        FILTER (

            Master,

            Master[UniqueID] = _ID

                && Master[EntryType] = "ForecastDate"

        ),

        [Date], DESC

    )

RETURN

    if(Master[EntryType] = "BaselineDate",DATEDIFF(MAXX(temp,[Date]),[Date],DAY),0)

Which seems to be working however can someone explain it to me as I'm struggling to understand how it is working 

I'm confused with the MAXX part and that when i try and return temp[Date] it says its not a table?

or suggest a simpler way of calculating this??

Thanks!

[bron12321 · Accepted solution]

After going away and coming back to it I've decided a new approach which I think works better:

Late2 =

VAR varCurrentScenarioID = Master[UniqueID]

VAR varCurrentEntryType = Master[EntryType]

VAR varCurrentDate = Master[Date]

VAR DateDifference =

IF(

    varCurrentEntryType = "ForecastDate",

    DATEDIFF(varCurrentDate,

        LOOKUPVALUE(Master[Date],Master[UniqueID],varCurrentScenarioID,Master[EntryType],"BaselineDate"),

        DAY),

    blank()

    )

VAR Result =  

IF(DateDifference < 0, "Late",BLANK())

RETURN

    Result