Display percentage values on a pie chart : <p>I am trying to draw a pie chart with ggplot2. My code is shown below.</p>

<pre><code>df &lt;- data.frame(
  variable = c("australia","hungary","germany","france","canada"),
  value = c(632,20,491,991,20)
)
ggplot(df, aes(x = "", y = value, fill = variable)) +
  geom_bar(width = 1, stat = "identity") +
  scale_fill_manual(values = c("red", "yellow","blue", "green", "cyan")) +
  coord_polar(theta = "y") +
  labs(title = "pie chart")
</code></pre>

<p>I would like to  display percentage values. How can I do that? </p>
