The Select Duplicate Rows() function was not in JMP 12. The below code should do what you want
Names Default To Here( 1 );
dt = Open( "$SAMPLE_DATA\Big Class.JMP" );
dt << sort( by( :Part_number ), order( ascending ), Replace Table( 1 ) );
dt << New Column( "dup",
formula(
If(
Row() == 1, value = 1,
:Part_number != Lag( :Part_number ), value = 1,
value
++);
value;
)
);
dt << select where( :dup > 1);
dt << delete rows;
dt << delete column( "dup" );
Jim