title: Labelling plots arranged with grid.arrange
body: <p>I have attached multiple plots to one page using grid.arrange.</p>
  
  <p>Is there a way to label each plot with "(a)","(b)" etc...</p>
  
  <p>I have tried using geom_text but it does not seem compatible with my plots....</p>
  
  <p><a href="https://i.stack.imgur.com/eJtYA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eJtYA.png" alt="my plots"></a></p>
  
  <p>.... as you can see, geom_text has some strange interaction with my legend symbols.</p>
  
  <p>I will show an example using the mtcars data of what I am trying to achieve. THe alternative to geom_text I have found is "annotate" which does not interact with my legend symbols. However, it is not easy to label only one facet....</p>
  
  <pre><code>q1=ggplot(mtcars, aes(x=mpg, y=wt)) + 
  geom_line() +
  geom_point()+
  facet_grid(~cyl)+
  annotate(geom="text", x=15, y=12, label="(a)",size=8,family="serif")
  
  q2=ggplot(mtcars, aes(x=mpg, y=wt,)) + 
  geom_line() +
  geom_point()+
  facet_grid(~cyl)+
  annotate(geom="text", x=15, y=12, label="(b)",size=8,family="serif")
  
  
  geom_text(x=15, y=5,size=8, label="(b)")
  
  gt1 &lt;- ggplotGrob(q1)
  gt2 &lt;- ggplotGrob(q2)
  
  
  grid.arrange(gt1,gt2, ncol=1)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/RWJ8B.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RWJ8B.png" alt="mtcars example"></a> </p>
  
  <p>Therefore, my question is, is there a way to label plots arranged using grid.arrange, so that the first facet in each plot is labelled with either a, or b or c etc...?</p>