title: Python Keep points in spline interpolation
body: <p>I wrote a code that performs a spline interpolation:</p>
  
  <pre><code>x1 = [ 0., 13.99576991, 27.99153981, 41.98730972, 55.98307963, 69.97884954, 83.97461944, 97.97038935, 111.9661593, 125.9619292, 139.9576991, 153.953469 ]
  y1 = [ 1., 0.88675318, 0.67899118, 0.50012243, 0.35737022, 0.27081293, 0.18486778, 0.11043095, 0.08582272, 0.04946131, 0.04285015, 0.02901567]
  
  x = np.array(x1) 
  y = np.array(y1)
  
  # Interpolate the data using a cubic spline to "new_length" samples
  new_length = 50
  new_x = np.linspace(x.min(), x.max(), new_length)
  new_y = sp.interpolate.interp1d(x, y, kind='cubic')(new_x)
  </code></pre>
  
  <p>But in the new dataset generated  <code>new_x</code> and <code>new_y</code> the original points are eliminated, only the first and the last values are kept. I would like to keep the original points.</p>