title: Filter dataframe on occurrence of same values across columns AND at column end
body: <p>I have a dataframe like this:</p>
  <pre><code>df &lt;- data.frame(
    id = 1:19,
    Area_l = c(1,2,0,0,0,2,3,1,2,0,0,0,0,3,4,0,0,0,0),
    Area_r = c(3,2,2,0,0,2,3,1,0,0,0,1,3,3,4,3,0,0,0)
  )
  </code></pre>
  <p>I need to filter the dataframe in such a way that all rows are omitted that fulfill two conditions:</p>
  <p>(i): <code>Area_l</code> and <code>Area_r</code> are <code>0</code></p>
  <p>(ii): the paired <code>0</code>values in <code>Area_l</code> and <code>Area_r</code> are the <strong>last</strong> values in the columns.</p>
  <p>I really have no clue how to implement these two conditions using <code>dplyr</code>. The <strong>desired result</strong> is this:</p>
  <pre><code>df
     id Area_l Area_r
  1   1      1      3
  2   2      2      2
  3   3      0      2
  4   4      0      0
  5   5      0      0
  6   6      2      2
  7   7      3      3
  8   8      1      1
  9   9      2      0
  10 10      0      0
  11 11      0      0
  12 12      0      1
  13 13      0      3
  14 14      3      3
  15 15      4      4
  16 16      0      3
  </code></pre>
  <p>Any help?</p>