Graphic size in slides

I'm doing a slide presentation with LaTeX, and some slides show only graphics. I created those graphics using R. But in those slides, the graphic size is too big and a part of the graphic does not appear in the slide, like it's been cropped. Is there any command in LaTeX that can make the graphic smaller in the slide?

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you can set the size of the graphic as an option, e.g.\includegraphics[width=0.5\textwidth]{mygraph} will scale the graph so that it is half of the current text width (and scale the height by the some amount). check the documentation for the graphicx package for this and other options available –  prettygully Nov 21 '11 at 2:38
I had the same problem. R Markdown to produce beamer presentation, wanted to include png images not created by R within the markdown doc. No control over size. A workable solution is to use the png library in R to read the images and plot inside a R chunk, giving you control over size via fig.width and fig.height. From this answer on stackoverflow –  andybega Feb 16 at 17:21

The \includegraphics command from the graphicx package can take a number of optional arguments, such as scale, width, and height. You can use these to get the desired size- a MWE follows

\documentclass{beamer}

\usepackage{graphicx}

\begin{document}
\begin{frame}
%\includegraphics[scale=0.5]{mypicture}
\includegraphics[width=2cm]{mypicture}
\end{frame}
\end{document}

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This doesn't work if you are trying to create beamer slides with R markdown. See my comment on the question for a solution. –  andybega Feb 16 at 17:23