title: Dates of a given weekday in R
body: <p>I want the dates of a given weekday (let´s say Fridays) between this two dates:</p>
  
  <pre><code>selectedMonths &lt;- c(  "201002",
                        "201103"
                      ) 
  </code></pre>
  
  <p>How can I store them in a data.frame, the desire results is:</p>
  
  <pre><code>    Date
  2010-02-05
  2010-02-12
  2010-02-19
  ...
  2011-03-04
  2011-03-11
  2011-03-18
  2011-03-25
  </code></pre>
  
  <p>I want to include the Fridays of the last date <code>"201103</code></p>