title: Set filter as ALL
body: <p>I am using a user form that their inputs makes a filter function of two parameters: the dataframe and the filter definition.
  Often I need ignore that filter, but I have to pass obligatorily for the user form. 
  What is the fillments I can assign it to get ALL the rows of the dataframe?</p>
  
  <pre><code>&gt; require (dplyr)
  &gt; a &lt;- data.frame(f1 = 1:10, f2 = 11:12)
  &gt; filter_by_f2 &lt;- function (a, filterlist) {
  +   filter(a,f2 %in% filterlist)
  + }
  &gt; filterlist &lt;- 11
  &gt; filter_by_f2 (a, filterlist)
    f1 f2
  1  1 11
  2  3 11
  3  5 11
  4  7 11
  5  9 11
  &gt; # I would like set filter that get all the rows
  &gt; filterlist &lt;- TRUE
  &gt; filter_by_f2 (a, filterlist)
  [1] f1 f2
  &lt;0 rows&gt; (or 0-length row.names)
  &gt; # need this result when I filtered
  &gt; a
     f1 f2
  1   1 11
  2   2 12
  3   3 11
  4   4 12
  5   5 11
  6   6 12
  7   7 11
  8   8 12
  9   9 11
  10 10 12
  </code></pre>