title: Subset data frame column using pipe and dot
body: <p>I want to learn how to properly use the "." when subsetting with magrittr. </p>
  
  <p>Given a dataframe <code>myDataframe</code>,</p>
  
  <pre><code>myDataFrame &lt;- data.frame(c(1,2,3,3,3,4,5), c(10,11,12,13,14,15,16))
  #  c.1..2..3..3..3..4..5. c.10..11..12..13..14..15..16.
  #1                      1                            10
  #2                      2                            11
  #3                      3                            12
  #4                      3                            13
  #5                      3                            14
  #6                      4                            15
  #7                      5                            16
  </code></pre>
  
  <p>I want to remove all rows with 3 in the first column, which I could do with <code>myDataFrame[ myDataFrame[,1] != 3 ,]</code> to get this result:</p>
  
  <pre><code>#  c.1..2..3..3..3..4..5. c.10..11..12..13..14..15..16.
  #1                      1                            10
  #2                      2                            11
  #6                      4                            15
  #7                      5                            16 
  </code></pre>
  
  <p>However, I need to do it with a pipe (and I can't name the columns of the dataframe).</p>
  
  <p>When I try to run <code>myDataFrame %&gt;% "[" (.[,1] != 3)</code> I get an "undefined columns selected" error. How do I select one column within a dataframe referred to with a dot?</p>