title: R - creating a complete data frame by combining from other data frames
body: <p>I am trying to create two new column of people's ages and their age groups(5 year intervals) given their date of birth from a data frame.
  The current data frame For example: </p>
  
  <pre><code>Person      Date of Birth 
  A             1/2/2000
  B             3/2/1998
  C             4/5/2008
  </code></pre>
  
  <p>The expected outcome is :</p>
  
  <pre><code>Person      Date of Birth     Age   Age-Group
  A             1/2/2000        18    15-20
  B             3/2/1990        28    25-30
  C             4/5/2008        10    5-10
  </code></pre>
  
  <p>What is the best way to do this on the most efficient way for a large data set? Thanks                            </p>