content: """
  ===========================================================
  Hierarchical clustering: structured vs unstructured ward
  ===========================================================
  
  Example builds a swiss roll dataset and runs
  hierarchical clustering on their position.
  
  For more information, see :ref:`hierarchical_clustering`.
  
  In a first step, the hierarchical clustering is performed without connectivity
  constraints on the structure and is solely based on distance, whereas in
  a second step the clustering is restricted to the k-Nearest Neighbors
  graph: it's a hierarchical clustering with structure prior.
  
  Some of the clusters learned without connectivity constraints do not
  respect the structure of the swiss roll and extend across different folds of
  the manifolds. On the opposite, when opposing connectivity constraints,
  the clusters form a nice parcellation of the swiss roll.
  """
  
  # Authors : Vincent Michel, 2010
  #           Alexandre Gramfort, 2010
  #           Gael Varoquaux, 2010
  # License: BSD 3 clause
  
  print(__doc__)
  
  import time as time
  import numpy as np
  import matplotlib.pyplot as plt
  import mpl_toolkits.mplot3d.axes3d as p3
  from sklearn.cluster import AgglomerativeClustering
  from sklearn.datasets.samples_generator import make_swiss_roll
  
  # #############################################################################
  # Generate data (swiss roll dataset)
  n_samples = 1500
  noise = 0.05
  X, _ = make_swiss_roll(n_samples, noise)
  # Make it thinner
  X[:, 1] *= .5
  
  # #############################################################################
  # Compute clustering
  print("Compute unstructured hierarchical clustering...")
  st = time.time()
  ward = AgglomerativeClustering(n_clusters=6, linkage='ward').fit(X)
  elapsed_time = time.time() - st
  label = ward.labels_
  print("Elapsed time: %.2fs" % elapsed_time)
  print("Number of points: %i" % label.size)
  
  # #############################################################################
  # Plot result
  fig = plt.figure()
  ax = p3.Axes3D(fig)
  ax.view_init(7, -80)
  for l in np.unique(label):
      ax.plot3D(X[label == l, 0], X[label == l, 1], X[label == l, 2],
                'o', color=plt.cm.jet(np.float(l) / np.max(label + 1)))
  plt.title('Without connectivity constraints (time %.2fs)' % elapsed_time)
  
  
  # #############################################################################
  # Define the structure A of the data. Here a 10 nearest neighbors
  from sklearn.neighbors import kneighbors_graph
  connectivity = kneighbors_graph(X, n_neighbors=10, include_self=False)
  
  # #############################################################################
  # Compute clustering
  print("Compute structured hierarchical clustering...")
  st = time.time()
  ward = AgglomerativeClustering(n_clusters=6, connectivity=connectivity,
                                 linkage='ward').fit(X)
  elapsed_time = time.time() - st
  label = ward.labels_
  print("Elapsed time: %.2fs" % elapsed_time)
  print("Number of points: %i" % label.size)
  
  # #############################################################################
  # Plot result
  fig = plt.figure()
  ax = p3.Axes3D(fig)
  ax.view_init(7, -80)
  for l in np.unique(label):
      ax.plot3D(X[label == l, 0], X[label == l, 1], X[label == l, 2],
                'o', color=plt.cm.jet(float(l) / np.max(label + 1)))
  plt.title('With connectivity constraints (time %.2fs)' % elapsed_time)
  
  plt.show()
  