Calculate cumulative reverse

Hello danilomorganti 

you can try this approach but it doesn't look on the date but really on the prior cell value. It basically adds a new column with the cumulative-column but shifted down by one row. After that a new column is added where your needed calculation takes place

Here a code example

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("Tc27DQAhDATRXhwjnT8Y3Aui/zbO0hKsNNFL5hxR+zpXNxmickeTE9mzYEvYJPOAJVlM2CLLBdtku2BFVv24Pw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Cumulative = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Cumulative", Int64.Type}}),
    GetNewColumnWithPreviousValue = Table.FromColumns
    (
        Table.ToColumns(#"Changed Type")&{{0}&List.RemoveLastN(#"Changed Type"[Cumulative])},
        Table.ColumnNames(#"Changed Type")&{"CumulativeShifted"}
    ),
    #"Added Custom" = Table.AddColumn(GetNewColumnWithPreviousValue, "Result", each [Cumulative]-[CumulativeShifted]),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom",{"CumulativeShifted"})
in
    #"Removed Columns"

Result

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

If this post helps or solves your problem, please mark it as solution (to help other users find useful content and to acknowledge the work of users that helped you)
Kudoes are nice too

Have fun

Jimmy

Hi, danilomorganti 

Based on your description, I created data to reproduce your scenario. The pbix file is attached in the end.

Table:

You may create a custom column as below.

let
tab=Table.SelectRows(#"Changed Type",(x)=>Date.Month(x[Date])=Date.Month([Date]) and x[Date]<[Date]),
m=try [Cumulative]-Table.Max(tab,"Date")[Cumulative] otherwise [Cumulative]-0
in 
m

Result:

Best Regards

Allan

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.