title: print surface fit equation in python
body: <p>I'm trying to fit a surface model to a 3D data-set (x,y,z) using matplotlib.<br>
  Where <code>z = f(x,y)</code>.<br>
  So, I'm going for the quadratic fitting with equation:  </p>
  
  <pre><code>f(x,y) = ax^2+by^2+cxy+dx+ey+f 
  </code></pre>
  
  <p>So far, I have successfully plotted the 3d-fitted-surface using least-square method using:  </p>
  
  <pre><code># best-fit quadratic curve    
     A = np.c_[np.ones(data.shape[0]), data[:,:2], np.prod(data[:,:2], axis=1), data[:,:2]**2]    
     C,_,_,_ = scipy.linalg.lstsq(A, data[:,2])    
     #evaluating on grid      
     Z = np.dot(np.c_[np.ones(XX.shape), XX, YY, XX*YY, XX**2, YY**2], C).reshape(X.shape)
  </code></pre>
  
  <p>But, how can I be able to print/get the fitted equation of the surface(with coefficient values) ? </p>
  
  <p>I little help will be highly appreciated.<br>
  thank you.</p>