Current month vs Previous month in pivot

[#1]

Hi, guys!

I have a table as follows:

Months	Jan-15
Business Group	FTE	Headcount	Current Month vs Previous Months
BG1	107.3	117	1
BG2	5.35	6	0
BG3	57.82	74	0
BG4	49.99	55	0
BG5	1.9	7	1
BG6	17.7	20	0
BG7	5.38	8	1

I needed to find the difference betwenn Current month and previous month. I solved the problem with the expression:Count(Employee)-Before(Count( Employee))

However when I filter the table for 1 month, for example for January, it doesnt show me the difference:

Months	Jan-15
Business Group	FTE	Headcount	Current Month vs Previous Months
BG1	107.3	117	-
BG2	5.35	6	-
BG3	57.82	74	-
BG4	49.99	55	-
BG5	1.9	7	-
BG6	17.7	20	-
BG7	5.38	8	-

Who knows what can be the reason of this problem?

[Gysbert_Wassenaar]

The problem is that you filtered the table. There's only on month left, so there's no month before that one month in the chart. There are ways to deal with that. See this document: Calculating rolling n-period totals, averages or other aggregations

[#3]

Thanks for the reply, but the link that is given above isnt quite clear

[#4]

Guys,

I'm trying the expression like :

Count (Employee) - Count({<Months={$(=Max([Months])-1)} >} [Employee])

but it doesnt work