n><span class="op">)</span></span>
<span><span class="co">#&gt; lvec is set to c(8, 16, 32, 64).</span></span>
<span><span class="co">#&gt; [1] 2.619107</span></span>
<span></span>
<span><span class="co"># standard deviation</span></span>
<span><span class="fu"><a href="../reference/fd.html">fd</a></span><span class="op">(</span><span class="va">surf</span>, method <span class="op">=</span> <span class="st">"sd"</span><span class="op">)</span></span>
<span><span class="co">#&gt; lvec is set to c(8, 16, 32, 