title: Factorize a numeric variable with Greek expression in labels in R
body: <p>Suppose the following data frame, I want to factorized var, and label numbers to Greek letters, from 1 to alpha, 2 to beta, 3 to gamma. But the following code does not work. </p>
  
  <pre><code>var&lt;-c(1,1,2,2,3,3)
  df&lt;-as.data.frame(var)
  df$var&lt;-factor(df$var, levels=c(1,2,3),
                 labels=c("1"=expression(alpha),
                          "2"=expression(beta),
                          "3"=expression(gamma)))
  </code></pre>
  
  <p>Why the final data frame is not greek letters but just text expressions? Can anyone help me on this? Thanks a lot.</p>