Can someone explain this DADX measure?

[Anonymous]

I am new to dax, and am having trouble trouble understanding this measure. Can someone who is familiar with dax break this down line by line and explain the code and functions? I feel it would be a great learning exercise for myself and perhaps others.

Actual =

VAR ACT = CALCULATE(SUM('COVID-19'[Cumulated]), LASTDATE('COVID-19'[Date]))

VAR PD = CALCULATE(CALCULATE(SUM('COVID-19'[Cumulated]), LASTDATE('COVID-19'[Date])),PREVIOUSDAY(LASTDATE('COVID-19'[Date])))

RETURN

IF (HASONEVALUE(TimeRange[Time Range]),

      SWITCH(VALUES(TimeRange[Time Range]),

              "Cumulated", ACT,

               "Daily", ACT - PD,

                BLANK()

      ),

      ACT

)

[Greg_Deckler · Accepted solution]

Well that is some interesting code.

ACT - Calculates the sum of the Cumulated column in table COVID-19 within the context of the last date (latest date) within the Date column in the same COVID-19 table. So, looks like it is getting the last value from what is probably an accumulating total column.

PD - So, they wrap the same calculation as above in another CALCULATE and tag in a filter context of PREVIOUSDAY from the last date so this is basically getting the next to the last day.

In the RETURN statement, they check to see if a single value has been selected in the Time Range column in the TimeRange table. Probably a slicer. Maybe a disconnected table? If there is only one value, then it returns ACT variable.

If that is not the case, it gets the distinct values that have been selected and here I am fairly sure it just returns BLANK or an error all the time as it is unclear to that you can compare a table to a string. I have tested this and you cannot.

[Chthonian]

Nice explanation @Greg_Deckler  got in there before me and with a more succinct answer than I had in my head 😊