How to calculate column by groups in Power Query

[LuciaS]

HI!

I am using this code to calculate my previous value from calculated column /(1+Rate) in Power Query 

Deflator = List.Transform(List.Skip(List.Accumulate(#"Changed Type3"[Rate], {1}, (s,c)=> s & {List.Last(s)/(1+c)})), Number.From),
Vlastné2= Table.FromColumns( Table.ToColumns(#"Changed Type3")& {Deflator}, Table.ColumnNames(#"Changed Type3")& {"Deflator"}),

I need to cacluĺate by groups so when there is different group it should start again with 1.

It should work like this 

Group          Value

 A                 B2=1/(1+A2)

 A                 B3=B2/(1+A3)

 A                 B4=B3/(1+A4)

 B                 B5=1/(1+A5)

 B                 B6=B5/(1+A6)

 B                 B7=B6/(1+A7)

Is there some way to calculate this by groups ? 

Thank you !

[LuciaS]

@wdx223_Daniel  Thank you !

[wdx223_Daniel · Accepted solution]

NewStep=Table.FromRecords(List.Accumulate(Table.ToRecords(#"Changed Type3"),{{},[]},(x,y)=>let a=Record.TransformFields(x{1},{y[Group],each (_??1)/(1+y[Rate])},2) in {x{0}&{y&[Deflator=Record.Field(a,y[Group])]},a}){0})

[LuciaS]

@wdx223_Daniel It works in Power Query but when I wanna use it in PBI there is error : Expression.Error: Evaluation resulted in a stack overflow and cannot continue.

Is there some way to fix it ?

[wdx223_Daniel]

your real data is too big to use this solution

you can try to group the data firstly

[LuciaS]

@wdx223_Daniel could end condition help ?