\begin{Schunk}
\begin{Sinput}
  str(dat)
\end{Sinput}
\begin{Soutput}
'data.frame':	19 obs. of  5 variables:
 $ grp: int  1 2 1 3 1 1 2 2 2 1 ...
 $ ed : int  11 10 9 15 7 12 8 6 11 20 ...
 $ inc: int  44444 34343 11112 23232 23111 78787 33233 22312 32322 76755 ...
 $ mar: Factor w/ 3 levels "N","W","Y": 3 3 1 1 3 1 3 1 3 1 ...
 $ sex: Factor w/ 2 levels "Fem","Mal": 2 1 2 1 1 2 2 1 1 1 ...
\end{Soutput}
\end{Schunk}
