title: grouping data by multiple columns
body: <p>I have many records of data to group by columns names.</p>
  
  <pre><code>Name  Surname  value
  al     adams    120
  al     adams    514
  al     bats     220
  al     bats     120
  bill   cox      440
  bill   cox      320
  bill   brit     320
  </code></pre>
  
  <p>I want to group by Name and Surname (and keep them), with the sum of Value.
  here is my code. I don't get the desired display.</p>
  
  <pre><code>DT&lt;-base_AA_P1 %&gt;%  select(Name, Surname) %&gt;% group_by(Name, Surname) %&gt;%  summarize(SUM_value = sum(value, na.rm = TRUE))
  </code></pre>