title: How to change correlation text size in ggpairs()
body: <p>I'm using <code>ggpairs()</code> in the <code>GGally</code> package. The pairs plot is of four continuous variables, and I gave another column, a factor with 2 levels, to a <code>colour</code> argument which worked very nicely, both coloring the points as I expected and (bonus!) in the upper-diagonal part of the plot reporting the correlations by that factor level. My only problem is that the text reporting the correlations is too small.</p>
  
  <p>Can I increase the size of the text reporting correlations in a <code>ggpairs()</code> plot?</p>
  
  <p>I tried giving a <code>cex</code> argument, it seems to have no effect. I'm already using <code>size</code> for yet another variable; it doesn't affect the text.</p>
  
  <p>For a specific example:</p>
  
  <pre><code>require(GGally)
  mtcars$cyl &lt;- as.factor(mtcars$cyl)
  ggpairs(mtcars, columns = c(1, 5), colour = "cyl")
  </code></pre>