urceCode" id="cb24"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb24-1"><a href="Intro.html#cb24-1"></a><span class="co"># Copy and paste </span></span>
<span id="cb24-2"><a href="Intro.html#cb24-2"></a>df<span class="op">$</span>a[df<span class="op">$</span>a <span class="op">==</span><span class="st"> </span><span class="dv">-99</span>] &lt;-<span class="st"> </span><span class="ot">NA</span></span>
<span id="cb24-3"><a href="Intro.html#cb24-3"></a>df<span class="op">$</span>b[df<span c