title: How to write if/else statements if dataframe is empty in R
body: <p>I am trying to do the following:
  If there is nothing in the dataframe, print "no_match". </p>
  
  <p>If there is something, bind it to the <code>ID</code> of dataframe <code>df2</code>: </p>
  
  <pre><code>if(df == []){
  print("nomatch")
  }else{
  cbind(df, df2$id2)
  }
  </code></pre>