(data lakes (12.2 65.2) (4.9 158) (0.46 175) (1.6 209))
(def rs (ys lakes))
(def volumes (calc 1000 * (xs lakes)))
(lines off)
(plot rs volumes)
(def rates (calc rs / volumes))
(plot rs rates)
(def relative-rates (/ (butlast rs) (rest rs)))