count values in previous months

[pgonin]

Hello dears!

May I ask you a pretty (hopefully) simple question.

Let's say I have a model consisting of period and id, like this:

period	id
2019-09	a
2019-09	b
2019-08	c
2019-08	d
2019-07	e
2019-07	f
2019-07	g
2019-06	h

And then, on a new app on a new sheet I want a pivot table with period as a dimension and count of id's for 3 previous periods as a measure: like this as a result

period	count of ids for 3 previous periods
2019-09	7
2019-08	6
2019-07	4
2019-06	1

How would one do so?

I don't want it to do in the load editor as this is a simple example, actual values rely on other filtered values, etc.

[Anil_Babu_Samineni]

Try 

RangeSum(Above(Count(id), 0, 3))