average of the last 12 month

[#1]

Hi!

I'm freshnew at QV community,

I d like to know how can calcultate the average of the last 12 month (including the active selction (month)) for 3 year

Thanks a lot for your help!

source table

                                                                         

Year	Month	Births
2012	1	265
2012	2	228
2012	3	271
2012	4	264
2012	5	230
2012	6	281
2012	7	270
2012	8	259
2012	9	293
2012	10	263
2012	11	278
2012	12	238
2013	1	266
2013	2	227
2013	3	246
2013	4	254
2013	5	244
2013	6	290
2013	7	269
2013	8	279
2013	9	278
2013	10	260
2013	11	241
2013	12	253
2014	1	289
2014	2	236
2014	3	282
2014	4	264
2014	5	249
2014	6	276
2014	7	303
2014	8	280
2014	9	262
2014	10	246
2014	11	271
2014	12

Hoped result

	Active month	Average of the last 12 months (including the active month
2012	263	263
2013	260	261
2014	246	265

[ecolomer]

Here you have an example

[#3]

Thanks Enrique for your help, however i can't open your document due to my licence policies.

It ll be very kind of you if you can explain me how can i figure out this exemple.

Best regards

[ecolomer]

Yes,

The formula for me in my example are:

='Last 12 months (AVG)= '& AVG({<YearMonth ={">=$(=Date(addmonths(Max(YearMonth), -12), 'MMM-YY')) <=$(=Date(addmonths(Max(YearMonth), -1),  'MMM-YY'))"} >} Sales)