an class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  xlim <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  pch <span class="op">=</span> <span class="fl">19</span>,</span>
<span>  cex <span class="op">=</span> <span class="fl">0.7</span>,</span>
<span>  xaxs <span class="op">=</span> <span class="st">"r"</span>,</span>
<span>  yaxs <span class="op">=</span> <span class="st">"r"</span>,</span>
<span>  <span class="va">...</span></span>
<span><span class="op">)</span></spa