="op">)</span></span>
<span><span class="co">#&gt; [1] "data.frame"</span></span>
<span><span class="co"># data.frames can contain matrices as variables, </span></span>
<span><span class="co"># thus becoming object linked lists of blocks.</span></span>
<span><span class="fu"><a href="https://rdrr.io/r/utils/str.html" class="external-link">str</a></span><span class="op">(</span><span class="va">potato</span><span class="op">[</span><span class="fl">1</span><span class="op">:</span><span class="fl">3</span><s