title: Combining rows with naming subsets
body: <p>I have a large <code>data.frame</code> (over 44,000 rows) which I have managed to <code>aggregate</code> into 128 rows that include my analysis <code>Section</code> and the sum of cells within that section presented as <code>Count</code>, an example of which looks like the following:</p>
  
  <pre><code>  Section   Count
    A - 2-1    10
    A - 2-2     2
    A - 2-3    39
    A - 2-4    31
    A - 2-5    42
    A - 2-6     1
    A - 2-7     9
    A - 2-8     4
    A - 2-9     2
    A - 3-1    52
    A - 3-2    27
    A - 3-3    42
    A - 3-4   107
    A - 3-5     6
    A - 3-6    51
    A - 3-7   155
    A - 3-8     5
    A - 3-9    13
  </code></pre>
  
  <p>I have looked at related topics but they all deal with having the same ID tag that makes it easy to group. What I want to do is to further aggregate so I can combine all of my <code>Sections</code> (e.g A-2) that have multiple fields (A-2-1, A-2-2, etc...) to give me a total cell <code>Count</code>, so that it appears as follows:</p>
  
  <pre><code>  Section       Count
    A - 2           140
    A - 3           458
  </code></pre>
  
  <p>I've been trying various ways of doing this based on other threads but cannot get any to work, so any help would be greatly appreciated!</p>