title: Principal Component Analysis - why eigenvectors' dot product aren't zeros?
body: <p>I try to do Principal Component Analysis of the breast_canser dataset using Python sklearn.
  And can't understand why both dot products (3 components) of eigenvectors aren't zeros?</p>
  
  <pre><code>frst = pca.components_[0,:]
  scnd = pca.components_[1,:]
  thrd = pca.components_[2,:]
  orth1 = np.dot(frst,scnd)
  orth2 = np.dot(scnd, thrd)
  print(orth1.real)
  print(orth2.real)
  </code></pre>
  
  <p>out:</p>
  
  <p>0.0</p>
  
  <p>1.52655665886e-16</p>