LaTeX whitespace not showing up in RMarkdown PDF

Question

I use rmarkdown and beamer to make teaching slides. I'm trying to insert a LaTeX equation in my slide, and this equation has a few spaces in it.

$Scott's \space pi = \frac{\% \space obs. \space agreements - \% \space exp. \space agreements}{1 - \% \space exp. \space agreements}$

When i hover on it with my cursor, Rstudio previews the equation correctly, as you can see in the screenshot below:

However, when I knit the PDF, the spaces don't appear, and I get this:

Am I missing something here?

My markdown header is as follows:

---
title: "XXXXXXXXXXXXXXXXXXXXXXXXXXXX"
author: "XXXXXXXXXXXXXXXXXXXXXXXXX"
institute: "XXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
date: "XXXXXX"
output:
  beamer_presentation:
    incremental: true
    theme: "Berlin"
    colortheme: "dove"
    fonttheme: "structurebold"
    includes:
      in_header: preamble.tex
classoption: "aspectratio=169"

---

The `preamble.tex' file is as follows:

\usepackage{caption}
\captionsetup[figure]{labelformat=empty}
\setbeamercolor{frametitle}{fg=white,bg=black} %section slide title
\setbeamercolor{section in foot}{fg=white, bg=black} % footsections
\setbeamercolor{part title}{fg=white, bg=black}
\setbeamertemplate{footline}
{
 \hbox{%
  \begin{beamercolorbox}[wd=.33\paperwidth,ht=2.6ex,dp=1ex,left,leftskip=2ex]{section in foot} % footsection 1
    \usebeamerfont{section in foot}\insertshortauthor
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.33\paperwidth,ht=2.6ex,dp=1ex,center]{section in foot} % footsection 2
    \usebeamerfont{section in foot} \inserttitle
  \end{beamercolorbox}%
  \begin{beamercolorbox}[wd=.34\paperwidth,ht=2.6ex,dp=1ex,right,rightskip=2ex]{section in foot} % footsection 3
    \usebeamerfont{section in foot} XXXXXXXXXXXXXXXXXXXXX
  \end{beamercolorbox}}%

  \vskip0pt%
}

\setbeamertemplate{section page}{
  \centering
  \begin{columns}
  \begin{column}{\paperwidth}
  \begin{beamercolorbox}[sep=12pt,center]{part title}
    \usebeamerfont{section title}\insertsection\par
  \end{beamercolorbox}
  \end{column}
  \end{columns}
}

Answer 1

Please don't ever use math mode for whole words, besides the missing spaces, the kerning is all messed up!

Instead you can use the \text{...} macro from the amsmath package (which is automatically loaded by beamer)

---
title: "XXXXXXXXXXXXXXXXXXXXXXXXXXXX"
author: "XXXXXXXXXXXXXXXXXXXXXXXXX"
institute: "XXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
date: "XXXXXX"
output:
  beamer_presentation:
    incremental: true
    theme: "Berlin"
    colortheme: "dove"
    fonttheme: "structurebold"
    includes:
      in_header: preamble.tex
classoption: "aspectratio=169"

---

- $\text{Scott's pi} = \frac{\text{\% obs. agreements} - \text{\% exp. agreements}}{1 - \text{\% exp. agreements}}$