class='st'>"DEATH"</span>, <span class='st'>"DEATH DUE TO PROGRESSIVE DISEASE"</span><span class='op'>)</span>,
                  stringsAsFactors <span class='op'>=</span> <span class='cn'>FALSE</span><span class='op'>)</span>

<span class='va'>QS1</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/r/base/data.frame.html'>data.frame</a></span><span class='op'>(</span>USUBJID <span class='op'>=</span> <span class='fl'>1</span>,
                  QSDTC   <span class='op'>=</span> 