Dax needed

Hi PowerBIBeginer ,

According to your description, I create a sample.

Here's my solution.

1.In Power Query, create a rank column, you can copy-paste the below code in a blank query to see the details.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ZdJLbsNADIPhu3idAiPNe9leI8j9r1GbLUSBA8ObD15EzP9+X17cvu7nel3f92vX5/WPHujEGliJLbARe2AnjsBBnIGTuAIXcQduohX++pI4HZWuMp5lcZfnBSo1fduo3MA6lSPYoHIFm1TOYIvKHWxTOYQXKpdwS1dwCs/H8TpP16UpPP1xfx//PNq1BujQHKBTe4AuDQK6tYhHa9EkoKZNQF2jgNajCnA7qgD3owrw0CqgU6uALq0CurWKR1vRKqCmVUBdq4BWrQLatApoP6oAj6MK8DyqAN/nfX4B", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Date Column" = _t, Type = _t, Value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date Column", type date}, {"Type", type text}, {"Value", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each Date.Month([Date Column])),
    #"Added rank"=Table.AddRankColumn(#"Added Custom","Custom2",{"Custom"}),
    #"Added Custom1" = Table.AddColumn(#"Added rank", "Rank", each [Custom2]+Date.Year([Date Column])-2021),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom1",{"Custom", "Custom2"})
in
    #"Removed Columns"

Result:

2.Sort the Date column by Rank column.

3.Create a new table with one column, containing all the types and "Diff". Then relate the two tables with type column.

4.Create a measure.

Measure =
IF (
    MAX ( 'Table (2)'[Type] ) = "Diff",
    MAXX ( FILTER ( ALL ( 'Table' ), 'Table'[Type] = "A" ), 'Table'[Value] )
        - MAXX ( FILTER ( ALL ( 'Table' ), 'Table'[Type] = "B" ), 'Table'[Value] ),
    MAX ( 'Table'[Value] )
)

Put Type from table2 in matrix columns and measure in matrix values, get the result.

I attach my file below for your reference.

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Best regards,

Community Support Team_yanjiang

Thank You for so detailed explanation and fantastic solution!.. Thank you for kind attention