Change the size of header panel in lattice plot
<p>I want to change the <code>header panel size</code> and also the <code>font size</code> of the <code>text</code> within that. Here is an example:</p>

<pre><code>library(lattice)
dat &lt;-data.frame(a=(rnorm(50)),b=(rnorm(50)),c=(c(rep("first",25),rep("second",25))))
xyplot(a~b|c, data=dat,par.settings = list(strip.background=list(col="gray")))
</code></pre>

<p>Basically I need the size of the <code>gray area</code> and also <code>"first"</code> and <code>"second"</code> font size to be larger.</p>