class="op">(</span><span class="va">tracks.seg</span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co">#select only id, tseg, SL, and TA columns</span></span></span>
<span class="r-in"><span><span class="va">tracks.seg2</span><span class="op">&lt;-</span> <span class="va">tracks.seg</span><span class="op">[</span>,<span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span cl