title: Convert LibSVM output to vector of floats
body: <p>I need to form <code>HOGDescriptor::setSVMDetector()</code> input.</p>
  
  <p>I compute descriptors with openCV then use libSVM to get model file.
  To form input i know that i need to get support vectors' values and elementwise mul them with alphas (then add -rho at the end), but <strong>i don't get where to get these alphas</strong>.</p>
  
  <p>I have a list of SVs like:</p>
  
  <pre><code>1 1:-0.0434783 2:0.153846 3:0.194444 4:-0.353712 5:-0.45054
  1 1:-0.2173916 2:-0.38461 3:0.222262 4:-0.676686 5:-0.78062
  </code></pre>
  
  <p>but where to get alphas?</p>