      PLoS ONE. 12.</span></a>
<a class="sourceLine" id="cb2-35" data-line-number="35"></a>
<a class="sourceLine" id="cb2-36" data-line-number="36">df &lt;-<span class="st"> </span><span class="kw"><a href="https://www.rdocumentation.org/packages/base/topics/data.frame">data.frame</a></span>(<span class="dt">stringsAsFactors=</span><span class="ot">FALSE</span>,</a>
<a class="sourceLine" id="cb2-37" data-line-number="37">      <span class="dt">gender =</span> <span class="kw"><a href="https://www.rdocumenta