DF = data.frame(
    type=as.factor( c( rep( 'A', 3 ), rep( 'B', 3 ), rep( 'C', 3 ), rep( 'D', 3 ) ) ),
    amount=c( 20, 40, 18, 75, 25, 21, 15, 30, 21, 25, 30, 31 )
)