\begin{Schunk}
\begin{Sinput}
 merge(x = datX, y = datY, by = "ID", all.x = TRUE)
\end{Sinput}
\begin{Soutput}
   ID cars      fear pets
1 111    6  90.61873    5
2 112    5  97.35806   NA
3 114    6  94.99807    8
4 115    5 106.76902    6
5 116    5 114.09072   NA
6  NA    7  91.15475    4
7  NA    7  91.15475    4
8  NA    9 109.50524    4
9  NA    9 109.50524    4
\end{Soutput}
\end{Schunk}
