"acid" <-
structure(list(carb = c(0.1, 0.3, 0.5, 0.6, 0.7, 0.9),
optden = c(0.086, 0.269, 0.446, 0.538, 0.626, 0.782)),
row.names = c("1", "2", "3", "4", "5", "6"), class = "data.frame")