title: Reverse filter/subset dataframe
body: <p>I have data that looks something like:</p>
  
  <pre><code>print(dat)
  i1  i2  node_id
   4   4        8
   4   5        8
   3   2        9
   5   1        8
  </code></pre>
  
  <p>Using either dplyr's <code>filter</code> or <code>subset</code>(preferably filter)  I would like to reverse filter the data so I get this:</p>
  
  <pre><code> print(dat)
   i1  i2  node_id
   4   4        8
   4   5        8
   5   1        8
  </code></pre>
  
  <p>I say reverse filter because instead of filtering or sub-setting like:</p>
  
  <pre><code>dat&lt;-filter(dat,node_id==8)
  dat&lt;-subset(dat,node_id==8)
  </code></pre>
  
  <p>I would like to do this by telling R I want to keep everything except where the node_id==9
  I have tried:</p>
  
  <pre><code>dat&lt;-filter(dat,-node_id==9)
  dat&lt;-subset(dat,-node_id==9)
  </code></pre>
  
  <p>But neither work.  Any suggestions?  Thanks.</p>