Calculating the Difference between columns in matrix visual

Hi GotData 

Without knowing how your data looks like, I assume that your data is like below in the table. 

You need to have a period sort table in the model with an Index column in chronological order. Connect this table to the source table on Period column. Then use this table's Period column in the matrix visual and the slicer visual. 

Then you can create measures like below

Difference in U = 
var _curPeriodIndex = MAX('Period Sort'[Index])
var _prePeriodIndex = CALCULATE(MAX('Period Sort'[Index]),ALLSELECTED('Period Sort'),'Period Sort'[Index] < _curPeriodIndex)
return
IF(ISBLANK(_prePeriodIndex),BLANK(),SUM('Table'[Units]) - CALCULATE(SUM('Table'[Units]),ALLEXCEPT('Table','Table'[Brand]),'Period Sort'[Index] = _prePeriodIndex))

Rank Difference = 
var _curPeriodIndex = MAX('Period Sort'[Index])
var _prePeriodIndex = CALCULATE(MAX('Period Sort'[Index]),ALLSELECTED('Period Sort'),'Period Sort'[Index] < _curPeriodIndex)
return
IF(ISBLANK(_prePeriodIndex),BLANK(),MAX('Table'[Rank]) - CALCULATE(MAX('Table'[Rank]),ALLEXCEPT('Table','Table'[Brand]),'Period Sort'[Index] = _prePeriodIndex))

%CT Difference = 
var _curPeriodIndex = MAX('Period Sort'[Index])
var _prePeriodIndex = CALCULATE(MAX('Period Sort'[Index]),ALLSELECTED('Period Sort'),'Period Sort'[Index] < _curPeriodIndex)
return
IF(ISBLANK(_prePeriodIndex),BLANK(),SUM('Table'[%CT]) - CALCULATE(SUM('Table'[%CT]),ALLEXCEPT('Table','Table'[Brand]),'Period Sort'[Index] = _prePeriodIndex))

The result:

You can use the slicer to select incontinuous periods. It will show the difference between selected periods correctly. 

The sample pbix file has been attached at bottom. Hope this helps. 

Best Regards,
Community Support Team _ Jing
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