
oriented circle shown above (the difference is that, different from
oriented ellipses, oriented circles are not close with respect to all
affine transformations).</p>

<p>For the oriented ellipse, this affine transformation $(A,T)$ is
encoded explicitly in the <code/>frame</code> vector used to represent
it numerically. For example, the code fragment</p>

<div class="highlight"><pre><span class="n">f</span> <span class="p">=</span> <span class="p">[</span><span class="n">T</span> <span class="p">;</span> <