title: Add a row to a matrix in OpenCV
body: <p>This is a very simple question but I couldn't find the answer in Google or in OpenCV documentation. How do you insert a row with either a vector or a default number at the bottom of a <code>cv::Mat</code>? I tried:</p>
  
  <pre><code>std::vector&lt;double&gt; v = {0, 0, 1};
  m.push_back(v);
  </code></pre>
  
  <p>which compiles, but it always gets me an assertion error. What is the right way to do it?</p>