Using DAX to return the Nth highest or lowest value

For 3rd largest:

With TOPN:

PHP Code: 

MINX(
    TOPN( 3, SUMMARIZE( Table1, Table1[Units] ), Table1[Units], DESC ),
    [Units]
) 


With RANKX:

PHP Code: 

VAR MyTable =
    SUMMARIZE(
        Table1,
        Table1[Units],
        "Rank", RANKX( ALL( Table1 ), Table1[Units] )
    )
RETURN
    MAXX( MyTable, IF( [Rank] = 3, [Units] ) ) 


Regards