Embed R plot in beamer frame using knitr

Question

I am trying to adjust the vertical alignment of a plot in a beamer object. Here is an example:

\documentclass{beamer}
% To change margins for all slides
\setbeamersize{text margin left=0.5cm,text margin right=0.5cm}

\begin{document}

\title{Title of talk}
\author{John Doe}

\maketitle

\begin{frame}[fragile]
\frametitle{Make a plot}

Code:
<<plot_something, fig.width=3.5, fig.height=3.5, fig.align='center'>>=
plot(1:100, rnorm(100), ylab = "Random value")
@

\end{frame}

\end{document}  

The position of the plot in the resulting .pdf file is too far down. How do I adjust the position so that the whitespace above the plot is used more efficiently?

Answer 1

I figured it out. The standard margins of a plot object are wide so resetting them does the trick:

\documentclass{beamer}
% To change margins for all slides
\setbeamersize{text margin left=0.5cm,text margin right=0.5cm}

\begin{document}

\title{Title of talk}
\author{John Doe}

\maketitle

\begin{frame}[fragile]
\frametitle{Make a plot}

Code:
<<plot_something, fig.width=3.5, fig.height=2, fig.align='center'>>=
par(mai=c(0.4,0.4,0.2,0.2))
plot(1:100, rnorm(100), ylab = "Random value")
@

\end{frame}

\end{document}