Two files contain information on patients of a weight loss clinic:
weightloss.dat contains header information, and weightlossd.dat
contains information recorded at each appointment for which the
patient came in.  The variables are:

weightloss.dat
   id   -- patient's unique identification number
   sex  -- patient's gender (F or M)
   age  -- patient's age in years at start of weightloss program

weightlossd.dat
   id     -- patient's unique identification number
   date   -- date on which weight was measured
   weight -- weight in pounds