title: How to select characters that are present in multiple columns of data
body: <p>I am trying to select all the characters in this data set to make a data frame of only the character shared in common between the three columns</p>
  
  <p>I tried using duplicated() from dyplr but that will only select duplicates from 2 of the columns.</p>
  
  <pre><code>#  UT          MT              HT
  ABHD17C       ABCG1       AC005884.1
  ABHD4         ABHD17C      AC009234.1
  ABO           ABO         AC011933.1
  AC009234.1    AC009234.1   AC097724.3
  ACSL3        AC025627.9    ABO
  ACSL5        AC097724.3    ACTA2
  ACSS1        ACP5         ADAMTS15
  ACTBP12      ACSS1        ADAMTS20
  ACTG1        ACSL5        ADH7
  ACTG1P12     ACSS1        AKR1C1
  ACTN4        ACTA2        AKR1C2
  ADAM19       ADAMTS15     AKR1C4
  ADAMTS15     ADAMTS20     ALDH1L2
  ADCK3        ADH7         ALDH3A1
  </code></pre>
  
  <p>In this example, the columns should only share "ABO", but in my more extensive data set characters are selected that are not in all three columns</p>