config = Birch::Config.new(
  2,                # number of dimensions of data points
  :manhattan,       # distance metric, only :manhattan is supported currently
  5.0,              # distance treshold
  3                 # branching factor
)

tree = Birch::Tree.new(config)
tree << [ 2.0, 2.0 ]
tree << [ 2.1, 2.5 ]
tree << [ 8.0, 8.0 ]
tree << [ 7.9, 7.9 ]
tree << [ 5.0, 5.2 ]

tree.root.children.length # == 3 - three clusters were created
tree.root.children[0].points_count # == 2 - first cluster has 2 points
tree.root.children[1].points_count # == 2 - second cluster also has 2 points
tree.root.children[2].points_count # == 1 - third cluster has 1 point