title: remove subsequent values in row in R
body: <p>I want to remove a specific repetitive value in each row in the dataframe.<br>
  let's say:  </p>
  
  <pre><code>DF (3*5)
  #  c1 c2 c3 c4 c5
  1  A  A  B  A  NA
  2  C  C  A  A  B
  3  B  A  A  NA NA
  </code></pre>
  
  <p>I want to remove subsequent A value.  </p>
  
  <pre><code>so New_df:
  #  c1 c2 c3 c4 c5
  1  A  B  A  NA NA
  2  C  C  A  B  NA
  3  B  A  NA NA NA
  </code></pre>
  
  <p>P.S. Column 5(c5) can be removed because all NA value.<br>
  The point is to remove only subsequent 'A' value, and other subsequent values should not be changed (e.g. the second row has two 'C' which should not be removed).<br>
  How can I do it in R?</p>