Parallelperiod () failing in a SUMMARIZE table .... but working otherwise

[charleshale]

I am using a relatively common measure for activesubs at any given period that simply counts  unique email addresses that were added before or equal to the last date in a period and didnt go inactive.

|1|ActiveSubs| =  
VAR _startofperiod = MIN ( DimDate[Date] )   --DimDate is a standard calendar table
VAR _endofperiod = MAX ( DimDate[Date] )
RETURN
    CALCULATE (
        DISTINCTCOUNT ( Table2[Email] ),
        Table2[Churn_DateAdded] <= _endofperiod,
        Table2[Churn_Hard+Soft90InactiveDate] > _endofperiod
        ),
        REMOVEFILTERS ( DimDate )
    ) 

This measure works just fine, including with time-shifting measures like PARALLELPERIOD() and and PREVIOUSMONTH().  However, oddly, it fails if I attempt a simple summarize such as

Test Table = AddColumns (
Summarize (Table2, DimDate[Year],
"Active Subs",   [|1|ActiveSubs|]),
"Active Subs Prior Yr",  Calculate ( [|1|ActiveSubs|] , PARALLELPERIOD (DimDate[Date],-1, YEAR)))

Specifically the "Active Subs Prior Yr" column remains blank. Has anyone ever seen this?   Is it that PREVIOUS_________ or PARALLELPERIOD require continuous days of a date table and that filter context doesnt get passed through in a SUMMARIZE where only a column of the date table gets summarized?

[charleshale · Accepted solution]

UPDATE: The source of the problem was an object conflict. 

[TheoC]

Hi @charleshale, may it be linked to the Summarize being on the DimDate[Year] (i.e. Year) and the Parallel Period being linked to a prior Month?  The Summarize function usually summarises the respective column from my understanding. I could be wrong, but this may be causing the issue.

Best of luck either way.

[charleshale]

Thanks, @theo.  I tried it as well with 

Test Table = Summarize (Table2, DimDate[Year],
"Active Subs",   [|1|ActiveSubs|],
"Active Subs Prior Yr",  Calculate ( [|1|ActiveSubs|] , PARALLELPERIOD (DimDate[Date],-1, YEAR))

And get the same issue.  

I wonder if SUMMARIZE () can't handle the data transposition between a data table columns if the SUMMARIZE use DimDate[Year] and a column calc calls for DimDate[Date]

[TheoC]

Hi @charleshale, no trouble at all!

A quick one, it may be my limited understanding on usability / functionality of the SUMMARIZE function, however, I thought the first component of the SUMMARIZE function needed to be the Table  that matched the column to be summarised?

[charleshale]

I'm no  expert  but just on PowerBI a ton and I routinely use SUMMARIZE() with all tables that are related  -- ie   SUMMARIZE (Table,  Table2[col1], Table8[col7]) -- although I reckon it isnt best practice when SUMMARIZECOLUMNS can be used.

And I certainly am able to get what I want with SUMMARIZCOLUMNS

AA_WBS2 = 
SUMMARIZECOLUMNS (
    DimDate[YearMonthnumber],
    "Subs", [|1|ActiveSubs|AP|],
    "Subs Prev Month1", [|1|ActiveSubs_#PriorMo|H&S|AP],
    "Subs Prev Month2", CALCULATE([|1|ActiveSubs|AP|], PREVIOUSMONTH(DimDate[Date])))

 with both a measure and PREVIOUSMONTH calc.....so I wonder if the error at top is about (A) SUMMARIZE not being able to work with full date table if only a column of that datetable is summarized, or (B) that, per msft documentation, for PREVIOUS[period] time intel functions to work, all dates need to be present for the years required.  

If I had to guess, I'd bet the issue a bit of both:   ie that PREVIOUS___________  can't work with a summary table that doesnt have Date[Date] as a component.    Has anyone ever used SUMMARIZE(   without Date[Date] and been able use PREVIOUS_____ as a function in the summarize table columns?

Any thoughts from the studio audience on this?