title: Change size of axes title and labels in ggplot2
body: <p>I have a really simple question, which I am struggling to find the answer to.  I hoped someone here might be able to help me.</p>
  
  <p>An example dataframe is presented below:</p>
  
  <pre><code>a &lt;- c(1:10)
  b &lt;- c(10:1)
  df &lt;- data.frame(a,b)
  library(ggplot2)
  g = ggplot(data=df) + geom_point(aes(x=a, y=b)) +
    xlab("x axis")
  g
  </code></pre>
  
  <p>I just want to learn how I change the text size of the axes titles and the axes labels.</p>