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scipy.cluster.hierarchy.

# num_obs_linkage

scipy.cluster.hierarchy.num_obs_linkage(Z)

  Return the number of original observations of the linkage matrix passed.

  Parameters:
    Z ndarray

      The linkage matrix on which to perform the operation.

  Returns:
    n int

      The number of original observations in the linkage.

  Notes

  `num_obs_linkage` has experimental support for Python Array API Standard compatible backends in addition to NumPy. Please consider testing these features by setting an environment variable `SCIPY_ARRAY_API=1` and providing CuPy, PyTorch, JAX, or Dask arrays as array arguments. The following combinations of backend and device (or other capability) are supported.

  Library | CPU | GPU
  --- | --- | ---
  NumPy | ✅ | n/a
  CuPy | n/a | ✅
  PyTorch | ✅ | ✅
  JAX | ✅ | ✅
  Dask | ✅ | n/a

  See Support for the array API standard for more information.

  Examples

      >>> from scipy.cluster.hierarchy import ward, num_obs_linkage
      >>> from scipy.spatial.distance import pdist

      >>> X = [[0, 0], [0, 1], [1, 0],
      ...      [0, 4], [0, 3], [1, 4],
      ...      [4, 0], [3, 0], [4, 1],
      ...      [4, 4], [3, 4], [4, 3]]

      >>> Z = ward(pdist(X))

  `Z` is a linkage matrix obtained after using the Ward clustering method with `X`, a dataset with 12 data points.

      >>> num_obs_linkage(Z)
      12