Averange from the last 12 months

[#1]

I've got table looking like this:

ReadingDate,=avg(Cost)

,£189.56

11/04/2011,£10.00

28/05/2011,£326.00

02/06/2011,£12.00

28/06/2011,£53.00

10/09/2011,£956.00

11/10/2011,£63.00

01/01/2012,£36.00

11/04/2012,£150.00

12/05/2012,£100.00

and i am able to make averange of single date, but how to make averange of the year, but not from january to december, but from ex. from may last year to may this year, so from the last 12 months?

[ramoncova06]

this will do it assuming you do have a valid date format

=Avg( {$<Date = {">=$(=AddMonths(Max(Date),-12)) <=$(=Max(Date))"} , NaN-={''NaN'}>} NaN)

if you have another date format let me know so I can tweak it the format to resemble yours

* Edited since I noticed that was missing the max(date) in the rolling last 12 months

[Anonymous]

try  this

AVG({$<ReagingDate = {"<=$(=addmonths(max(ReagingDate),-1))>=$(=addmonths(min(ReagingDate),-12))",NaN-={'NaN'}}>}Cost)