title: Adding extra time points to data frame
body: <p>I have a data frame that has patients "ID", "TIME", "DV", "AMT", "EVID: event ID", "MDV: missing DV" and several patients covariates as below.</p>
  
  <pre><code>df
  ID    TIME   DV   AMT   MDV   EVID   WT   SEX
  9010   0     NA    50    1      1    70    0
  9010   0.5   0.2   0     0      0    70    0
  9010   1     5     0     0      0    70    0
  9010   5     10    0     0      0    70    0
  9011   0     NA    50    1      1    60    1
  9011   1     4     0     0      0    60    1
  9011   3     6     0     0      0    60    1
  9011   6     10    0     0      0    60    1
  </code></pre>
  
  <p>I need to add a <strong>unique</strong> "TIME" sequence for each subject ID in addition to the times included in the "df".</p>
  
  <pre><code>timeseq &lt;- c(seq(0.05,5,by=0.1))
  </code></pre>
  
  <p>For the rows of added times, "DV=NA; AMT=0; MDV=0; EVID=0". The "ID ; WT; SEX" should stay the same. </p>
  
  <p>I need help in how to add these extra time points to my data frame using R. I have huge dataset and the sampling times points are different between subjects.</p>