title: Merging two data frames, while keeping uncommon rows between them using R
body: <p>I have two <code>dfs</code> as below and want to merge. I want to merge these two dfs based on the family column and add the count for each gene without removing the genes in the final df if they are not common between the first df and the second one.</p>
  
  <pre><code>#first df
  Family &lt;- c("LET-7","LET-7","LET-7","MIR-10","MIR-103","MIR-124","MIR-124","MIR-124")
  Sequence &lt;- c("ATCGGCA","ATGCTAC","ATCGGCA","ATCGTTT","TGAGGAG","TGATCAG","AATTCAG","AATTCAG")
  my_data_frame &lt;- data.frame(Family,Sequence)
  </code></pre>
  
  <pre><code>#second df
  counts &lt;- c("2","3")
  Family &lt;- c("LET-7","MIR-124")
  countdf &lt;- data.frame(Family,counts)
  </code></pre>
  
  <p>the output that I want to have </p>
  
  <pre><code>Family &lt;- c("LET-7","LET-7","LET-7","MIR-10","MIR-103","MIR-124","MIR-124","MIR-124")
  Counts &lt;- c("2","2","2","0","0","3","3","3")
  Sequence &lt;- c("ATCGGCA","ATGCTAC","ATCGGCA","ATCGTTT","TGAGGAG","TGATCAG","AATTCAG","AATTCAG")
  newdf &lt;- data.frame(Family,Counts,Sequence)
  </code></pre>