% From: https://support.rstudio.com/hc/en-us/community/posts/202717656-Can-we-have-columns-in-rmarkdown-beamer-presentations-
% 
% In the YAML header of your Rmd file, add a reference to a tex file to add to the tex file preamble ;
% 
% output: 
%   beamer_presentation:
%     includes:
%       in_header: mypreamble.tex
% 
% In mypreamble.tex, add:
% 
% \def\begincols{\begin{columns}}
% \def\begincol{\begin{column}}
% \def\endcol{\end{column}}
% \def\endcols{\end{columns}}
% 
% Finally, in the Rmd file, use this kind of syntax:
% 
% ## Two Column Layout
% 
% \begincols
%   \begincol{.48\textwidth}
% 
% This slide has two columns.
% 
%   \endcol
% \begincol{.48\textwidth}
% 
% ```{r pressure}
% plot(pressure)
% ```
% 
%   \endcol
% \endcols
\def\begincols{\begin{columns}}
\def\begincol{\begin{column}}
\def\endcol{\end{column}}
\def\endcols{\end{columns}}