1 ## load the nhanes data
   2 load()
   3 
   4 ## how many observations, how many variables?
   5 ## how many males/females
   6 ## nrow(), ncol(), table(), dim()
   7 
   8 
   9 
  10 ## how old are the participants (summary statistics, mean, sd)
  11 
  12 
  13 
  14 
  15 ## plot waistcf vs age
  16 require(ggplot)
  17 
  18 
  19 
  20 
  21 
  22 ## model the respective data in a linear model,
  23 ## extract and interpret the coefficients.
  24 ## Extract also the confidence intervals.
  25 ## lm(), coef(), confint()
  26 
  27 
  28 
  29 
  30 
  31 ## add sex as a covariate. interpret. 
  32 
  33 
  34 
  35 
  36 
  37 
  38 ## add sex as a covariate. interpret. (including interaction)
  39