title: R Shiny Reactive values, dplyr filter error?
body: <p>I am trying to figure out as I select input in UI to immediately reflect the results on page.
  My search results led me to look into reactive expression and reactive values. But as I am trying to filter the value on data, I think it is causing some complication yet I have no clue what I am supposed to do with this.</p>
  
  <p>It seems like the filter function doesn't seem to work though.</p>
  
  <p>This is the error message:</p>
  
  <pre><code>Warning: Error in UseMethod: no applicable method for 'filter_' applied to an object of class "c('reactiveExpr', 'reactive')"
  Stack trace (innermost first):
      51: filter_
      50: filter.default
      49: filter
      48: function_list[[i]]
      47: freduce
      46: _fseq
      45: eval
      44: eval
      43: withVisible
      42: %&gt;%
      41: eval
      40: makeFunction
      39: exprToFunction
      38: observe
      37: server 
       1: runApp
  Error in UseMethod("filter_") : 
    no applicable method for 'filter_' applied to an object of class "c('reactiveExpr', 'reactive')"
  </code></pre>