title: Problem with mathematical expression annotation in ggplot2
body: <p>I want to make the following anotation in a ggplot graph</p>
  
  <p><a href="https://i.stack.imgur.com/o6V4W.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o6V4W.gif" alt="enter image description here"></a></p>
  
  <p>I am triying this</p>
  
  <pre><code>ggplot(data = data.frame(x = c(0, 70)), aes(x)) +
    stat_function(fun = dchisq, args = list(df = 30))+
    annotate("text", x = c(7), y = c(0.019), 
             label = "P(16.791&lt;=chi[70]^{2}&lt;46.979)==0.95",parse = TRUE , size=4 , fontface="bold")
  </code></pre>
  
  <p>And getting the following error</p>
  
  <pre><code>Error in parse(text = as.character(lab)) : &lt;text&gt;:1:22: inesperado '&lt;'
  1: P(16.791&lt;=chi[70]^{2}&lt;
                           ^
  </code></pre>
  
  <p>Why the first "&lt;=" is parsed but the second "&lt;" doesn't</p>