title: Figure labels: add text on graphs in the same location despite figure size
body: <p>I want to know how it's possible to add a letter to reference a graph in R, but without always changing the y and x value. I want the text to be always at the same place (on the same baseline, and at the same relative distance on the x axis. </p>
  
  <pre><code>set.seed(1234)
  plot(2,3)
  text(x = 1.5,y = 4, "A", font = 2 )
  plot(rnorm(100))
  text(x = 1.5,y = 2, "B", font = 2)
  </code></pre>
  
  <p>As you can see, the letter B is not at the same distance on the x axis and it's a little down. I would like this to be adjusting automatically when I resize the graphic window in RStudio. 
  <a href="https://i.stack.imgur.com/AVC3l.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AVC3l.png" alt="enter image description here"></a></p>