s="op">==</span><span class="st"> &quot;b&quot;</span>] &lt;-<span class="st"> </span><span class="dv">15</span><span class="op">:</span><span class="dv">13</span> <span class="co"># (2) -- subassign in column &#39;c&#39;</span></span></code></pre></div>
<p>both (1) and (2) resulted in deep copy of the entire data.frame in versions of <code>R</code> versions <code>&lt; 3.1</code>. <a href="https://stackoverflow.com/q/23898969/559784">It copied more than once</a>. To improve performance by avoiding these red