ChickWeight: Weight versus age of chicks on different diets
Description
The ChickWeight data frame has 578 rows and 4 columns from an
  experiment on the effect of diet on early growth of chicks.Format
An object of class
  c("nfnGroupedData", "nfGroupedData", "groupedData", "data.frame")
  containing the following columns:
  
    - weight
 - 
      a numeric vector giving the body weight of the chick (gm).
    
 
    - Time
 - 
      a numeric vector giving the number of days since birth when
      the measurement was made.
    
 
    - Chick
 - 
      an ordered factor with levels
      
18 < … < 48
      giving a unique identifier for the chick.  The ordering of
      the levels groups chicks on the same diet together and
      orders them according to their final weight (lightest to
      heaviest) within diet.
     
    - Diet
 - 
      a factor with levels 1, …, 4 indicating which
      experimental diet the chick received.
    
 
  
Details
The body weights of the chicks were measured at birth and every
  second day thereafter until day 20.  They were also measured on day
  21.  There were four groups on chicks on different protein diets. This dataset was originally part of package nlme, and that has
  methods (including for [, as.data.frame, plot and
  print) for its grouped-data classes.See Also
SSlogis for models fitted to this dataset.