Change default font in ggplot2
<p>So this is a series of questions really. I would like to change the default font in <code>ggplot2</code>, and I understand the easiest way is to change the default family in <code>theme_gray</code>. </p>

<p>But I am puzzling how to do that. I can do this:</p>

<pre><code>&gt; theme_set(theme_gray(base_size = 18))
</code></pre>

<p>But I can't do this:</p>

<pre><code>&gt; theme_set(theme_gray(family="mono"))
Error in theme_gray(family = "mono") : unused argument (family = "mono")
</code></pre>

<p>And then when I look at the help, I wonder if I shouldn't be using <code>theme_update</code> as I am only changing one member. And then I see that it also mentions under "See also": </p>

<pre><code>%+replace% and +.gg
</code></pre>

<p>And I wonder if I should be using those instead. Of course I could not get them to work either...</p>

<p>So what works? And more importantly, what <strong><em>should</em></strong> one be using to keep up in the fast changing <code>ggplot2</code> world?</p>