title: How to use a variable in quotes in r?
body: <pre><code>q=c('01','02','03')
  url="example.com/date=q[1]"
  url
  # [1] "example.com/date=q[1]"
  </code></pre>
  
  <p>What I really want <code>url</code> to be is "example.com/date=01".</p>
  
  <p>What should I do?</p>