Find % difference between two columns in matrix table

1. Make sure your format is Date for the column "Month"

2. Add a new column MonthNb

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjDUByIjAyMTJR0lQwMDpVgdiKARTNASIWYMV2gEFIwFAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Month = _t, Value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Month", type date}, {"Value", Int64.Type}}),
    #"Inserted Month" = Table.AddColumn(#"Changed Type", "MonthNb", each Date.Month([Month]), Int64.Type)
in
    #"Inserted Month"

3. Close Power Query and change the format of the column Month

4. Add the DAX measures:

Diff MoM = 
VAR _CurrentValue = SUM(YourTableName[Value])
VAR _vTable = 
OFFSET(
    -1,
    ALL(
        YourTableName[Month],
        YourTableName[Value],
        YourTableName[MonthNb]
    ),
    ORDERBY(YourTableName[Month], ASC),
)

VAR _Selection = 
SELECTCOLUMNS( _vTable, YourTableName[Value])

VAR _PreviousValue = SUMX(_Selection, YourTableName[Value])
VAR _Difference = IF(_PreviousValue <> BLANK() ,_PreviousValue-_CurrentValue)

RETURN 
_Difference

============================
%Diff MoM = 
VAR _CurrentValue = SUM(YourTableName[Value])
VAR _vTable = 
OFFSET(
    -1,
    ALL(
        YourTableName[Month],
        YourTableName[Value],
        YourTableName[MonthNb]
    ),
    ORDERBY(YourTableName[Month], ASC),
)

VAR _Selection = 
SELECTCOLUMNS( _vTable, YourTableName[Value])

VAR _PreviousValue = SUMX(_Selection, YourTableName[Value])
VAR _Difference = IF(_PreviousValue <> BLANK() ,_PreviousValue-_CurrentValue)

RETURN 
DIVIDE(_Difference, _PreviousValue)


==================
SumValue = SUM('YourTableName'[Value])

5. Use a Matrix column with the column Month on Columns and SumValues, Diff MoM and %Diff MoM

In the format pane choose Values/ Options/ Switch values to rows ON

Result

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