</div>
<div id="section" class="section level1">
<h1></h1>
<p>With <em>data.table’s</em> <code>:=</code> operator, absolutely no copies are made in <em>both</em> (1) and (2), irrespective of R version you are using. This is because <code>:=</code> operator updates <em>data.table</em> columns <em>in-place</em> (by reference).</p>
<div id="b-the-operator" class="section level3">
<h3>b) The <code>:=</code> operator</h3>
<p>It can be used in <code>j</code> in two ways:</p>
<ol style="list-style-type: lower-al