title: Add text to individual facets in ggplot
body: <p>I wonder how I put different text in individual facets. I want to add the text <strong><em>inside</em></strong> the plot using <code>annotate</code> or <code>geom_text()</code> I know there are duplicated posts in this, but I don't manage to get it correct. Here is my data:</p>
  
  <pre><code>Experiment         FC           Pairing
  Meister et al. -2.74236520      yes
  Meister et al. -0.7436354       no
  Meister et al. -2.74236520      yes
  Meister et al. -0.73536354      no
  daub et al.    -0.64246768      yes
  daub et al.    -0.6663321       no
  daub et al.    -0.64246768      yes
  daub et al.    -0.6663321       no
  hans et al.    -2.32230716      yes
  hans et al.    -0.49423279      no
  hans et al.    -2.32723716      yes
  hans et al.    -0.4944279       no
  
  ggplot(combined_pos1,aes(Pairing,FC,fill=as.factor(Pairing))) + 
        geom_boxplot(fill = "grey90") +  coord_cartesian(ylim=c(-3,3)) + 
        facet_grid(~Experiment)
  </code></pre>