title: Using ggplot geom_text when combining superscript and variable label that contains < symbol
body: <p>I am having trouble adding R2 annotations to a faceted plot, where my R2 values are sometimes &lt;0.01 (yes, it's not a good regression). I would like the 2 of R2 to be superscript.
  I have tried several options but seem to be stymied by the &lt; symbol in my values</p>
  
  <p>eg, using the iris data set, I first set up a new data frame with my R2 values previously calculated. The x &amp; y positions are also set up as these are different for every facet (not essential for the iris dataset, but it is for mine)</p>
  
  <pre><code>SEr2s &lt;- data.frame(Species = c("virginica",  "setosa",  "versicolor" ), 
                    xpos = c(5,7,7), ypos = c(4.2, 2, 4.2), 
                    lab = c("&lt;0.01","0.08", "0.05"))
  </code></pre>
  
  <p>Then I run my plot:</p>
  
  <pre><code>XYPlot&lt;-ggplot(data = iris, aes(x=Sepal.Length)) + 
    geom_point(aes(y = Sepal.Width), colour="grey40")+
    geom_smooth(aes(y = Sepal.Width), col="grey40", lwd=0.5, method="lm", se=FALSE) +
    geom_text(data = SEr2s, size=3, vjust=0, hjust=0,
              aes(x = xpos,  y = ypos, 
               label = paste("r^2==",lab)), parse = TRUE)+
    theme_bw() +
    theme(strip.background = element_blank(), strip.placement = "outside",
          panel.grid.minor = element_blank(), legend.position = "right") +
    facet_wrap(~Species)
  </code></pre>
  
  <p>I get this error:</p>
  
  <blockquote>
    <p>Error in parse(text = text[[i]]) : :1:7: unexpected '&lt;'
    1: r^2== &lt;
              ^</p>
  </blockquote>
  
  <p>Is there a way to change my code or my labelling dataframe so that it doesn't try to evaluate these symbols? </p>