title: Join two data frames together and use most recent result as rows added
body: <p>I am trying to achieve the 'Final.Data' output shown below.</p>
  
  <p>We start with the Reference data and I want to add the 'Add.Data' but join on the 'Person' and return the most recent result prior to the reference (date).</p>
  
  <p>I am looking for dplyr, data.table or sql solutions in r.</p>
  
  <p>I then want to be able to reproduce this for 1000s of entries, so looking for a reasonable efficient solution.</p>
  
  <pre><code>library(tibble)
  Reference.Data  &lt;-  tibble(Person = "John",
                             Date = "2019-07-10")
  
  Add.Data &lt;- tibble(Person = "John",
                     Order.Date = c("2019-07-09","2019-07-08") ,
                     Order = 1:2)
  
  Final.Data &lt;- tibble(Person = "John",
                       Date = "2019-07-10",
                       Order.Date = "2019-07-09",
                       Order = 1)
  </code></pre>