title: Create column in dataframe in R that shows progressive tally
body: <p>I have a data frame in R that I'm attempting to create a column that tallies ascending starting at zero up to the max count for that individual.</p>
  
  <p>I use the following code in R to structure my data into a dataframe then attempt to create a "count up" column. My code, however, is creating a single tally not a sequence and it is returning multiple rows, not grouped, for the same record. </p>
  
  <pre><code>ncUseData &lt;- select(rollData, session, UID, name)
  
  ncUseData &lt;- ncUseData %&gt;% group_by(session, UID) %&gt;% mutate(countUp = n())
  </code></pre>
  
  <p>My expected results I'm hoping to look like this. I'm hoping to get a sequence of increasing counts. </p>
  
  <pre><code>session, UID, name, countUp
  80, aa52, bob, 0
  81, aa52, bob, 1
  82, aa52, bob, 2
  83, aa52, bob, 3
  84, aa52, bob, 4
  85, aa52, bob, 5
  10, x87y, jill, 0
  11, x87y, jill, 1
  12, x87y, jill, 2
  13, x87y, jill, 3
  14, x87y, jill, 4
  15, x87y, jill, 5
  </code></pre>