<span class="r-in"><span>     panel.first <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/graphics/abline.html" class="external-link">abline</a></span><span class="op">(</span>h <span class="op">=</span> <span class="va">at_y</span>, col <span class="op">=</span> <span class="st">"grey80"</span><span class="op">)</span>,</span></span>
<span class="r-in"><span>     main <span class="op">=</span> <span class="st">"US Total Natural Gas Consumption"</span>,</span></span>
<span class="r-in"