title: compare two dataset and create a new dataframe by looking at the union of both dataset
body: <p>I have two dataframe df1 and df2, i want to create a new dataframe by looking at the union of the two dataset. If a particular column has value 1 in both dataset, the new dataset should have value 1 for that particular column. </p>
  
  <pre><code>    df1 = data.frame( V1 = letters[1:5], V2 = c("0","1","1","0","1"), V3 = c("0","0","0","0","1"), V4 =c("1","1","1","1","1"), V5 = c("0","0","0","0","1"),V6 =c("1","1","1","0","0"))
  
      df2 = data.frame( V1 = letters[1:5], V2 = c("1","1","1","0","0"), V3 = c("1","0","0","0","1"), V4 =c("0","0","1","0","1"), V5 = c("1","0","0","0","1"))
  
     result = data.frame( V1 = letters[1:5], V2 = c("1","1","1","0","1"), V3 = c("1","0","0","0","1"), V4 =c("1","1","1","1","1"), V5 = c("1","0","0","0","1"),V6 =c("1","1","1","0","0"))
  </code></pre>