Average line in Line chart

[#1]

Hi,

I have line chart which shows multiple trend line as per the second dimension. In addition to that I need a one more line which should show average sales.

Dimensions used:

1. Year-Month

2. City

Example used:

SUM({SPP<MonthEndDate={">=$(=vlast12Months)"}>}Sales)

Advance thanks!!

[sunny_talwar]

May be this:

Avg(TOTAL Aggr(Sum({SPP<MonthEndDate={">=$(=vlast12Months)"}>}Sales), Year-Month, City))