Fetch data from previous row

Hey ArvindJha ,
I use the below DAX to create a calculated column 

WEIGHT_ = 
var currentPatientID = 'Table'[PATIENTID]
var currentSite = 'Table'[SITE]
var prevDate = 
    maxx(
        SELECTCOLUMNS(
            FILTER(
                WINDOW(
                    1, abs, -1, rel,
                    SUMMARIZE(
                        ALLSELECTED( 'Table' ), 
                        'Table'[PATIENTID],
                        'Table'[SITE],
                        'Table'[DATE],
                        'Table'[WEIGHT]
                    ),
                    ORDERBY( 'Table'[DATE] , ASC),
                    PARTITIONBY( 'Table'[PATIENTID] , 'Table'[SITE])
                ),
                NOT( ISBLANK( 'Table'[WEIGHT] ) )
            ),
            "d" , [DATE]
        )
        , [d]
    )
return
CALCULATE(
    MAX('Table'[WEIGHT]),
    ALL('Table'),
    'Table'[PATIENTID] = currentPatientID,
    'Table'[SITE] = currentSite,
    'Table'[DATE] = prevDate
)

The table looks like this

Hopefully, this provides what you are looking for.
If not, read this article: https://www.minceddata.info/2024/03/09/my-favorite-windowing-function-window/

Regards,

Tom