)</span>
<span id="cb2-5"><a href="#cb2-5" tabindex="-1"></a></span>
<span id="cb2-6"><a href="#cb2-6" tabindex="-1"></a><span class="co"># Basic operations</span></span>
<span id="cb2-7"><a href="#cb2-7" tabindex="-1"></a>vol_mean <span class="ot">&lt;-</span> <span class="fu">mean</span>(vol)</span>
<span id="cb2-8"><a href="#cb2-8" tabindex="-1"></a>vol_sd <span class="ot">&lt;-</span> <span class="fu">sd</span>(vol)</span>
<span id="cb2-9"><a href="#cb2-9" tabindex="-1"></a><span class="fu">cat</span>(<