><span class="r-pr">#&gt;</span>     event_no</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>        &lt;int&gt;</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  1:       NA</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  2:       NA</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  3:       NA</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  4:       NA</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  5:       NA</span>
<sp