\begin{Schunk}
\begin{Sinput}
 library(kutils)
 mergeCheck(df1, df2, by = "id")
\end{Sinput}
\begin{Soutput}
Merge difficulties detected

Unmatched cases from df1 and df2 :
df1 
  id          x
1  1 -0.9806329
7  7  0.2239254
df2 
  id          x
6  9 -0.3116061
7 10  1.5561096
\end{Soutput}
\end{Schunk}
