Slicer to select current month as default

Hi,

According to your description, I create a table to test:

Please take following steps:

1)create a calculated table:

Slicer =

UNION (

    VAR t =

        DISTINCT (

            ADDCOLUMNS (

                SELECTCOLUMNS ( 'Table', "Month Year", FORMAT ( 'Table'[Date], "MMMM YYYY" ) ),

                "minDate", CALCULATE (

                    MIN ( 'Table'[Date] ),

                    FILTER ( 'Table', [Month Year] = FORMAT ( 'Table'[Date], "MMMM YYYY" ) )

                )

            )

        )

    RETURN

        SELECTCOLUMNS (

            ADDCOLUMNS ( t, "Rank", RANKX ( t, [minDate],, ASC, DENSE ) ),

            "Month Year", [Month Year],

            "Rank", [Rank]

        ),

    DATATABLE ( "Month Year", STRING, "Rank", INTEGER, { { "Last Month", 0 } } )

)

And it shows:

2)create a measure:

IsFiltered =

IF (

    FORMAT ( SELECTEDVALUE ( 'Table'[Date] ), "MMMM YYYY" )

        IN FILTERS ( Slicer[Month Year] ),

    1,

    IF (

        "Last Month" IN FILTERS ( Slicer[Month Year] ),

        IF (

            SELECTEDVALUE ( 'Table'[Date] )

                >= DATE ( YEAR ( TODAY () ), MONTH ( TODAY () ) - 1, 1 )

                && SELECTEDVALUE ( 'Table'[Date] )

                    < DATE ( YEAR ( TODAY () ), MONTH ( TODAY () ), 1 ),

            1,

            -1

        ),

        -1

    )

)

3)choose table visual and set measure ‘IsFiltered’ as 1:

4)choose column ‘Month Year’ of table ‘Slicer’ as a slicer:

5)choose the ‘Last Month’ and the result shows:

Here is my test pbix file:

pbix 

Best Regards,

Giotto Zhi