title: iframe of a shinyapp in rmarkdown
body: <p>I am trying to embed a shinyapp in an rmarkdown file, if possible in full screen. Checking other answers, I tried this that works for this youtube:</p>
  
  <pre><code>---
  title: "Derek Corcoran"
  ---
  
  Some text
  
  &lt;iframe width="560" height="315" src="http://www.youtube.com/embed/9bZkp7q19f0?rel=0" frameborder="0" allowfullscreen&gt;&lt;/iframe&gt;
  
  Some more text
  </code></pre>
  
  <p>but when I try with my shiny app it does not work:</p>
  
  <pre><code>---
  title: "Derek Corcoran"
  ---
  
  Some text
  
  &lt;iframe width="560" height="315" src="https://derek-corcoran.shinyapps.io/WhereShouldYouLive/" frameborder="0" allowfullscreen&gt;&lt;/iframe&gt;
  
  Some more text
  </code></pre>
  
  <h2>Some other options I tried:</h2>
  
  <pre><code>---
  title: "Derek Corcoran"
  ---
  
  Some text
  
  &lt;iframe width="560" height="315" src="https://derek-corcoran.shinyapps.io/WhereShouldYouLive/"&gt;&lt;/iframe&gt;
  
  Some more text
  </code></pre>
  
  <p>I just get an empty square</p>
  
  <pre><code>---
  title: "Derek Corcoran"
  ---
  
  Some text
  
  &lt;iframe src="https://derek-corcoran.shinyapps.io/WhereShouldYouLive/"&gt;&lt;/iframe&gt;
  
  Some more text
  </code></pre>
  
  <p>Smaller empty square.</p>
  
  <p>Any ideas</p>