get exact coordinates of animating element with d3.js
<p>In this <a href="http://jsbin.com/qizovu/edit?html,js,output" rel="nofollow">jsbin</a>, I am trying to position the horizontal line to the smaller circle in the animating group but the jsbin is using getBoundingClientRect and some arbitrary values to get there.</p>

<p>I wanted to use this value:</p>

<pre><code>d3.select('.circle-guide').attr('cx')
</code></pre>

<p>But it always returns the same value and does not take the transform into account.</p>

<p>How can I get the coordinates of a n animating element?</p>