title: parse two signs (==4==2*2) in ggplot2's annotate
body: <p>Is there a simply way to parse two equal signs in the same text in ggplot2's annotate or do I have to annotate twice? (i.e. replace <code>:</code> by <code>=</code> in the plot below?)</p>
  
  <p>I can plot with annotate like this</p>
  
  <pre><code>require(ggplot2)
  f &lt;- data.frame(x = c(0, 1/1.1), y = c(1/.9, 0))
  c &lt;- ggplot(f, aes(x, y))
  c + stat_smooth(method = "lm", se=F)  
  + annotate("text", x=.6,y=.75, label=(paste0("slope:","frac(1, f[1])==", 
  coef(lm(f$y ~ f$x))[2])), parse=TRUE)
  </code></pre>
  
  <p>Which gives me this,
  <a href="https://i.stack.imgur.com/tke2d.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tke2d.png" alt="===="></a></p>
  
  <p>but I cannot have two equal signs like this,</p>
  
  <pre><code>f &lt;- data.frame(x = c(0, 1/1.1), y = c(1/.9, 0))
  c &lt;- ggplot(f, aes(x, y))
  c + stat_smooth(method = "lm", se=F)  + annotate("text", x=.6,y=.75,
  label=(paste0("slope==","frac(1, f[1])==", coef(lm(f$y ~ f$x))[2])), parse=TRUE)
  </code></pre>
  
  <p>I get this error.</p>
  
  <pre><code>Error in parse(text = lab) : &lt;text&gt;:1:23: unexpected '=='
  1: slope==frac(1, f[1])==
                            ^
  </code></pre>
  
  <p>In my real case I have several fractions, I realize that my working example is very simply and one might ask why replace <code>:</code> by <code>=</code>, but it's a working example.</p>