Ferritin concentration changes.
data(Ferritin)
A data frame with 20 rows (one per patient) and 3 columns:
The patients' ferritin content (in micrograms/L) in September
The patients' ferritin content (in micrograms/L) in March
The reduction in the patients' ferritin content (in micrograms/L) between September and the following March, during which time they had treatment