citation of surface plasmon-polaritons.</p>
<div class="sourceCode"><pre class="sourceCode r"><code class="sourceCode r">limits &lt;-<span class="st"> </span><span class="kw">ddply</span>(m, .(L1), summarize, 
                <span class="dt">xmin=</span><span class="kw">min</span>(x), <span class="dt">xmax=</span><span class="kw">max</span>(x), <span class="dt">ymin=</span><span class="op">-</span><span class="ot">Inf</span>, <span class="dt">ymax=</span><span class="ot">Inf</span>)

  <span class="kw">ggp