Calculate only the first month of a selected period

[LucyN]

Hi,

I have a table of Rates by Rate Dates (Rate Dates= [Rate Date.autoCalendar.YearMonth])

I want to calculate Delta % between the current month and the previous month

Delta= (current month Avg Rate - previous month Avg Rate)/previous month Avg Rate

But I don't want to calculate Delta for the first month of the selected time range (leave it Blank). What should I do?

(In the screenshot, I don't want to calculate Delta % of 2017-Nov)

[Kushal_Chawda]

@LucyN  If your Month field is in proper date format then you can try below expression for %Delta

=if(date(min(total Month),'YYYY-MMM')=Month, null(), %DeltaExpression)

[LucyN]

Hi Kush,

Thanks for your response. It didn't work quite well (it's may be because my Month field format). 

This is my data set (the data goes from 11/01/2017 to 11/01/2019)

This is what I'm trying to achieve.