title: Specify Font type on R Markdown
body: <p>How can I specify a font type i.e <code>Tahoma</code> on R Markdown. I am using the following to define my document</p>
  
  <pre><code>---
  bibliography: bibliography.bib
  csl: nature.csl
  documentclass: article
  fontsize: 12pt
  linkcolor: blue
  mainfont: Arial
  output: 
    pdf_document:
      fig_caption: Yes
  
  ---
  </code></pre>
  
  <p>How can I also specify the font size of figure captions -- like for the figure below</p>
  
  <pre><code>![Figure 2: The impact of malaria disease the factors within the bednet that in turn affect infections and other health issues](climate_change.png)
  </code></pre>