How to add calculated column?

[Anonymous]

Hi all, I have a data on customers payments by months:

Account_number	01/01/2018	01/02/2018	01/03/2018	01/04/2018
1	1000	2000	3000	1000
2	3000	3000	3000	3000
3	1000	1000	1000	2000

I want to compare between the column of last month to the average of the other months. something like this:

Account_number	01/01/2018	01/02/2018	01/03/2018	01/04/2018	Average(1-3/18)	last month/Avarge(previous 3 months)
1	1000	2000	3000	1000	2000	50%
2	3000	3000	3000	3000	3000	100%
3	1000	1000	1000	2000	1000	200%

How I do this? thanks!

[ChennaiahNallani]

Current Month:

Sum({<Year=, Quarter=, Month=, Week=, Date={‘>=$(=MonthStart(Max(Date)))<=$(=Max(Date))’}>} Sales)

Previous Month:

Sum({<Year=, Quarter=, Month=, Week=, Date={‘>=$(=MonthStart(Max(Date), -1))<=$(=MonthEnd(Max(Date), -1))’}>} Sales)

Hope this helps you.