ill touch up on this again in the <em>data.table design</em> vignette.</p>
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<li><p>When we store the column names on to a variable, e.g., <code>DT_n = names(DT)</code>, and then <em>add/update/delete</em> column(s) <em>by reference</em>. It would also modify <code>DT_n</code>, unless we do <code>copy(names(DT))</code>.</p>
<div class="sourceCode" id="cb19"><pre class="sourceCode r"><code class