\begin{Schunk}
\begin{Sinput}
 head(datX)
\end{Sinput}
\begin{Soutput}
   ID Year Quarter       pop illnesses
1 USA 1990      Q1  9.113642  84.02290
2 USA 1990      Q2  9.668422 118.05098
3 USA 1991      Q1 11.120713  95.18353
4 USA 1991      Q2 10.298724 106.20380
5  UK 1990      Q1 10.779622 106.12123
6  UK 1990      Q2 11.455785  98.37689
\end{Soutput}
\begin{Sinput}
 head(datY)
\end{Sinput}
\begin{Soutput}
  Country year Semester percipitation      cars
1     USA 1990       Q1     12.049190 111.28511
2     USA 1990       Q2     11.632446  76.19642
3     USA 1991       Q1     10.254271  89.39734
4     USA 1991       Q2     10.491188 109.37141
5      UK 1990       Q1      9.675913 108.54452
6      UK 1990       Q2      8.337950 114.60729
\end{Soutput}
\end{Schunk}
