title: Resize a matrix to a double array
body: <p>I have a std matrix A such as </p>
  
  <pre><code>std::vector&lt;std::vector&lt;double&gt; &gt; A(9,std::vector&lt;double&gt;9);
  </code></pre>
  
  <p>and to calculate its inverse i need to define it as a double of a size [1*81] such as </p>
  
  <pre><code>double newA[1*81];
  </code></pre>
  
  <p>is there a function like <em>resize</em> that I can do this conversion from a matrix to a double without a for loop?? </p>
  
  <p>Thanks in advance. </p>