Calculate difference between two fields that user selected

[njiang126]

I have pivot table, the value is count of items has been sold for each month for the past 24 months. 

User wants to select two months data to compare the difference, for example, user select 2020 January and 2021 January, how to add the third column that can calculate the difference , which is 1826-1027 for the first row?

Thanks, 

Nicole 

[melissapluke]

Hi,

You can add a "before" to your count.

Your first expression is your normal count('field')

Your "Difference" expression is count('field')-before(count('field')).

You can see in my example below, it shows the difference between the two. 

That said, it can get a bit overwhelming if you do not limit your selections. It suggest having a filter for your user to select the appropriate month-year they'd like to compare and then set the calculated condition to only calculated when getselectedcount('datefield')=2