Difference between 2 columns

[Rana]

I have a Matrix in PowerBI which is showing data for 2 months (month is a string not a date column like Aug, Sept or any selected 2 months). Matrix shows me Total for both months, instead of Sum i need the difference (reduction or addition) between 2 months. Is it doable?

[leonardmurphy]

No, a Matrix couldn't work with a subtraction formula in place of the totals. 

How would the matrix know whether you want to subtract Aug from Sep vs. Sep from Aug (given the months are strings)? What would you want to happen if a person picks 3 or more months instead of just 2? 

A measure would probably be your way forward. You could create a measure that subtracts a previous month value for any given month. But it wouldn't work dynamically with any two random months.

[Rana]

Everything you said I already have in my mind, you can do this simply in Excel but not in Power BI, stumped a bit.

[Rana]

I actually was able to do that in Tableau, it has an option to get a differencial between values in a Matrix. I just had to hide the 1st selected Month.

[leonardmurphy]

I don't know how that feature works in Tableau...but I can see why you'd want to do such a thing. 

Even in Excel though, you'd have to do the calculation outside of a single pivot table, wouldn't you?

Perhaps an opportunity for a custom visualization (one that allows you to select & then does a side-by-side comparison of 2 selected dates/categories/other attributes)

[Rana]

Yes in Excel it we created 3 pivot tables, 2 for each months and 3rd for differential. Can we do something similar in Power BI?

[Tsanka]

It seems that you are interested in data for 2 specific months (perhaps current month and the previous month). I would solve your task by adding 3 new measures - one to sum the values for the current month, the second - for the previous month and the 3rd - for the difference. Those measures can be visualized either in a table or in a matrix (with no fields placed in the column area)

PS: While me writing the above comment you have posted the screenshot with your matrix. I don't quite understand your example as requirements and structrure. Therefore please ignore my idea for a solution posted before

[Rana]

Tsanka,

1st column for a particular Date shows total number of Employees, 2nd column is the difference. So in the case of 1st month in the table it shows the same number as it doenst have anything to compare with (should be 0). All other months shows the difference between the month with the previous month.

[Tsanka · Accepted solution]

 @Rana,

A much cleaner code than the one posted by me before (and deleted) is the following:

PreviousDay = CALCULATE
(
  SUM (FactData[Employees]);
  Filter (ALL(FactData[Date]);FactData[Date]=Max(FactData[Date])-1)
)

Difference = IF(
   ISBLANK([PreviousDay]);
   0;
   SUM(FactData[Employees])-[PreviousDay]
)

[Rana]

It is sort of working in Power BI but for 1st month in the list it shows the same number. Screen shot below:

[Betissa]

Hello Rana,How did you calculate this field ?