Calculating average inventory by adding the begin amount and the end amount and then dividing by 2

Hi JoyceW ,

Is there any index field in your table? If this is a case, you can write formula to use index to find out correspond begin value and end value, then use them to get average. 

AVG Measure =
VAR _start =
    MINX ( ALLSELECTED ( Table[index] ), [index] )
VAR _end =
    MAXX ( ALLSELECTED ( Table[index] ), [index] )
RETURN
    DIVIDE (
        LOOKUPVALUE ( Table[Amount], Table[index], _start )
            + LOOKUPVALUE ( Table[Amount], Table[index], _end ),
        2,
        BLANK ()
    )

Otherwise you need to add index column first.(power bi data model not contains row/column index to find out first or last row value)

Regards,

Xiaoxin Sheng