Repeat steps multiple times over the same table

Hi donpep0 ,

An alternate approach to the situation. I am using Replace.Value instead of List.Accumulate.

Also, I don't use the index column.

Starting Point:

Code:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("NczBDQAhCETRVjacTRRRlFqM/bexgJnDvzwmnENcrfZOhTji1uiWQx2aF7aZKlAJFUscwBHYWFIndHq631cFaqRvuYDLS9mQ7X1JBrJH9wc=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Index = _t, Volume = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Index", Int64.Type}, {"Volume", Int64.Type}}),
    
    //Replace null with average of previous four periods
    #"Replaced Value" = Table.ReplaceValue(
                            #"Changed Type", 
                            each null, 
                            each 
                                let 
                                    LastFourPeriods = Table.SelectRows(
                                                            #"Changed Type", 
                                                            (x)=> x[Date] < [Date] and x[Date] >= Date.AddDays([Date], -4)
                                                        )[Volume], 
                                    FourPeriodAverage = List.Average(
                                                            List.RemoveNulls(LastFourPeriods)
                                                        ) 
                                in 
                                    FourPeriodAverage, 
                            Replacer.ReplaceValue,
                            {"Volume"}
                        )
in
    #"Replaced Value"

Outcome:

Regards

KT