title: Combine result from top_n with an "Other" category in dplyr
body: <p>I have a data frame <strong>dat1</strong></p>
  
  <pre><code>   Country Count
  1      AUS     1
  2       NZ     2
  3       NZ     1
  4      USA     3
  5      AUS     1
  6      IND     2
  7      AUS     4
  8      USA     2
  9      JPN     5
  10      CN     2
  </code></pre>
  
  <p>First I want to sum "Count" per "Country". Then the top 3 total counts per  country should be combined with an additional row "Others", which is the sum of countries which are not part of top 3.</p>
  
  <p>The expected outcome therefore would be:</p>
  
  <pre><code>    Country Count
  1     AUS     6
  2     JPN     5
  3     USA     5
  4     Others  7
  </code></pre>
  
  <p>I have tried the below code, but could not figure out how to place the "Others" row.</p>
  
  <pre><code>dat1 %&gt;%
      group_by(Country) %&gt;%
      summarise(Count = sum(Count)) %&gt;%
      arrange(desc(Count)) %&gt;%
      top_n(3)
  </code></pre>
  
  <p>This code currently gives:</p>
  
  <pre><code>    Country Count
  1     AUS     6
  2     JPN     5
  3     USA     5
  </code></pre>
  
  <p>Any help would be greatly appreciated.</p>
  
  <pre><code>dat1 &lt;- structure(list(Country = structure(c(1L, 5L, 5L, 6L, 1L, 3L, 
      1L, 6L, 4L, 2L), .Label = c("AUS", "CN", "IND", "JPN", "NZ", 
      "USA"), class = "factor"), Count = c(1L, 2L, 1L, 3L, 1L, 2L, 
      4L, 2L, 5L, 2L)), .Names = c("Country", "Count"), class = "data.frame",     row.names = c("1", 
      "2", "3", "4", "5", "6", "7", "8", "9", "10"))
  </code></pre>