title: Making pie chart's contours smoother on Shiny
body: <p>I am trying to have a nice looking plot for two (or possibly more) continuous values in the form of a pie chart using <code>ggplot2</code>.<br>
  The code is the following :  </p>
  
  <pre><code>library("ggplot2")
  library("ggthemes") ## for theme_economist
  df &lt;- data.frame(origin=c('with','without'),value=c(24536,50456))  
  pie &lt;- ggplot(df, aes(x = "",y=value, fill = origin))+  
      geom_bar(width = 1,stat="identity")+  
      coord_polar(theta = "y",start=pi/3)+  
      theme_economist()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/Xi92P.png" alt="pie"><br>
  The pie is relatively fine except that the contours of the pie seems to be a bit irregularly drawn.Of course when you export it as a pdf it looks fine but displayed in RStudio or Shiny it doesn't look nice at all.<br>
  Is there a way to change the resolution of the ggplot object directly or to make <code>renderplot()</code> aware that we want to display the image at a high resolution ?
  I tried modifying the <code>res</code> argument of the <code>renderPlot()</code> function but it distorts the image and do not get rid of the irregularity of the border.  </p>
  
  <p>How to make the contours of the pie smoother on Shiny or RStudio directly ? Thanks.</p>