Struggling with Current and Same period Last year only working without a date in the visual

[DebbieE]

really struggling (Still with time based intellicege

I have total Persons which is basically a distinct ount of people ID

And I have People this snapshot

In the date table I have a flag against the latest snapshot date used and then my dax is 

No People Latest Census = CALCULATE (

   [Total People],

    'Fact','Dim Date ('[latest Snapshot] = 1)

And I have a Same Period Last Year 

No People Same Period Last Year = CALCULATE([Total People]

                                            ,SAMEPERIODLASTYEAR('Dim Date'[Date])

                                    )

I eventually want a measure showing the difference between current and last period

[No People Latest Census] - [No People Same Period Last Year]

 And i want to display this in a visual

However. When i add a table like this everything is fine

date              Total People    Lastest Period   Last Period   Difference

01/01/22       100

01/01/23       150                            150             100                50

But withough the date I get this

Latest  Period   last Period Difference

 150                    250            100                

And Basically in the visual I only want to show the difference and Last period is just summing everything up without the Date in here

How do you deal with SAMEPERIODLAST year when your visual cant hold the actual date in it? Im really struggling with the concepts behind this?

Im essentially wanting a chart to just show changes

[SEMattis · Accepted solution]

@DebbieE, the reason why you are struggling is that you have to think of the context in which SAMEPERIODLAST is operating. When you remove the date column the measure in which you apply the SAMEPERIODLAST looses track of context and then sums all rows of your data in the last period, hence the 150 (Latest period) + 100 (Previous Period).

If you want to compare the date of your most recent snapshot to the same period the previous year you could also 

try something like this: 

VAR LYear = CALCULATE(MAX('Dim Date'[Date]) - 365, '[latest Snapshot] = 1')

Then add the variable to your filter in the calculate function under the RETURN statement as follows:

RETURN

 CALCULATE([Total People]

                                            ,'Dim Date'[Date] = LYear

                                    )

Hopefully it gives you what you want, though it is a bit hard coded.

[DebbieE]

I have gone for Flags in the Date Dimenion for this specific issue. 

Thanks for that

[SEMattis]

No problem at all.