title: "Preview in Window" does not work in RStudio
body: <p>In Rstudio, how can I see my plots in "Preview in Window" instead of "Preview in Viewer Pane" ? I already have changed setting as:</p>
  
  <pre><code> tools---global optinos---R Markdown----show output preview in window
  </code></pre>
  
  <p>But, still it does not work.</p>