How to calculate a Moving Range Average for a Xmr Chart

[#1]

Hello,

I am trying to build a Xmr Chart with the data below. There is an Month/Year filter and I always calculate the Average and the Moving Range Average with the selected data only*.

But I am having a hard time to calculate de Moving Range Average, I always get an erron on the expression.

Year/Month	Sales	Average *	Moving Range	Moving Range Avg
2012/10	100.038,59	105.023,83	17.884,04	??
2012/09	82.154,55	105.023,83	38.539,28	??
2012/08	120.693,83	105.023,83	3.485,48	??
2012/07	117.208,35	105.023,83	-	??

The Average I used the expression:  sum(total(Sales))/GetSelectedCount(Year/Month)

For the Moving Range:  fabs(sum(Sales)-below(sum(Sales)))

And for the Moving Range Avg I tried unsucessfully to use: sum(total(fabs(sum(Sales)-below(sum(Sales)))/GetSelectedCount(Year/Month)

Can anyone help me please?

Thank you very much.

[#2 · Accepted solution]

Could you try

Avg(total aggr(fabs(sum(Sales)- below(sum(Sales))),Year/Month))

^ This  will avg across thel range with values (count = 3)

OR

Avg

(total aggr(rangesum(fabs(sum(Sales)- below(sum(Sales)))),Year/Month

))

^ This one will avg across the full range (count = 4)

[#3]

Ryan,

Thank you very much for you help. I used the first expression and it worked great.