title: Append to an array within a specific index
body: <p>I've been really stumped for a while on this.
  I have a loop like this:</p>
  
  <pre><code>for(var i = 0; i &lt; Quotes.length; i++) {
      var timestamp = new Date().getTime();
      dataSets.push([[ timestamp, Quotes[i].unitprice ]]);
  }
  </code></pre>
  
  <p><code>dataSets</code> should be an array of <code>timestamp</code> and price data (<code>Quotes[i].unitprice</code>). Timestamp and price data is also an array which should be appended to for each stock; every update cycle when this loop is called.</p>
  
  <p>How can I append to an array contained within a specific dataSets index. </p>
  
  <p>Currently dataSets is defined in global scope as <code>dataSets = [[]]</code>. </p>
  
  <p>I just want to be able to update the inner array on each index (<code>dataSets[i]</code>).</p>
  
  <p>Any help is much appreciated. Thank you.</p>
  
  <p>EDIT: Say I have the stock quotes FOO and BAR; I want to be able to append to their index within <code>dataSets</code>. So where <code>dataSets[0]</code> is FOO and <code>dataSets[1]</code> is BAR,  I want to be able to update the timestamp and unit price array from [[134484, 1.40]] to [[134484, 1.40],[134487, 1.45]]</p>