\begin{Schunk}
\begin{Sinput}
 df1
\end{Sinput}
\begin{Soutput}
  idx           x
1   1 -0.44803329
2   2  0.32112354
3   3 -1.23017225
4   4 -1.32405869
5   5  1.26124227
6  NA  1.31923172
7 NaN -0.08075376
\end{Soutput}
\begin{Sinput}
 df2
\end{Sinput}
\begin{Soutput}
  idy           x
1   2 -0.50508981
2   3 -0.05215359
3   4  0.62886063
4   5  2.18000240
5   6 -0.06901731
6   9  1.54486360
7  10  1.32145202
\end{Soutput}
\end{Schunk}
