\begin{knitrout}
\definecolor{shadecolor}{rgb}{0.969, 0.969, 0.969}\color{fgcolor}\begin{kframe}
\begin{alltt}
\hlstd{df}\hlopt{$}\hlstd{rost}
\end{alltt}
\begin{verbatim}
## [1] 160 175 155 190  NA
\end{verbatim}
\begin{alltt}
\hlstd{df[ ,}\hlnum{1}\hlstd{] ; df[}\hlnum{4}\hlstd{,]}
\end{alltt}
\begin{verbatim}
## [1] 160 175 155 190  NA
##   rost ves
## 4  190  85
\end{verbatim}
\end{kframe}
\end{knitrout}