Infinity error

Hi,

According to your description, i create three tables to test:

Please take following steps:

1)Create a measure:

Measure = DIVIDE(COUNTROWS(Registrations),SUM(Regions[Population]))

Choose a matrix visual and it shows:

2)Create another measure:

Measure 2 =
VAR d =
    SELECTEDVALUE ( 'Year-Month'[Year-Month] )
RETURN
    IF (
        COUNTROWS ( 'Registrations' ) = 0,
        VAR t =
            FILTER (
                SUMMARIZE (
                    FILTER ( ALLSELECTED ( 'Year-Month' ), 'Year-Month'[Year-Month] < d ),
                    'Year-Month'[Year-Month].[Year],
                    'Year-Month'[Year-Month].[MonthNo],
                    "Number", CALCULATE ( COUNTROWS ( 'Registrations' ) )
                ),
                [Number] > 0
            )
        RETURN
            CALCULATE (
                [Measure],
                FILTER (
                    ALLSELECTED ( 'Registrations' ),
                    'Registrations'[Region] IN FILTERS ( 'Registrations'[Region] )
                        && MONTH ( 'Registrations'[Year-Month] ) = MAXX ( t, [Year-Month].[MonthNo] )
                        && YEAR ( 'Registrations'[Year-Month] ) = MAXX ( t, [Year-Month].[Year] )
                )
            ),
        [Measure]
    )

And it replace the original blank with previous month's data, the result shows:

Here is my test pbix file:

pbix 

Best Regards,

Giotto ZHi