Reference previous row in group by soft table

[Anonymous]

Hello All, I have use the group by feature to place an index for the sub tables. What I am trying to do is to get the each row within the a sub table to referenc the previous rows " Bench mark date of accomplishment" column. 

is this possible in power query? 

[Greg_Deckler · Accepted solution]

@Anonymous See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586.
The basic pattern is:
Column = 
  VAR __Current = [Value]
  VAR __PreviousDate = MAXX(FILTER('Table','Table'[Date] < EARLIER('Table'[Date])),[Date])

  VAR __Previous = MAXX(FILTER('Table',[Date]=__PreviousDate),[Value])
RETURN
 ( __Current - __Previous ) * 1.

This is the general pattern. Not sure I am clear on the requirement.