nt_richness_df</span><span class="op">)</span><span class="op">[</span><span class="fl">5</span><span class="op">:</span><span class="fl">21</span><span class="op">]</span></span>
<span></span>
<span></span>
<span><span class="co">#creating cluster</span></span>
<span><span class="va">my.cluster</span> <span class="op">&lt;-</span> <span class="fu">parallel</span><span class="fu">::</span><span class="fu"><a href="https://rdrr.io/r/parallel/makeCluster.html" class="external-link">makeCluster</a></span><span