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Module « scipy.cluster.hierarchy »

Fonction from_mlab_linkage - module scipy.cluster.hierarchy

Signature de la fonction from_mlab_linkage

def from_mlab_linkage(Z) 

Description

help(scipy.cluster.hierarchy.from_mlab_linkage)

Convert a linkage matrix generated by MATLAB(TM) to a new
linkage matrix compatible with this module.

The conversion does two things:

 * the indices are converted from ``1..N`` to ``0..(N-1)`` form,
   and

 * a fourth column ``Z[:,3]`` is added where ``Z[i,3]`` represents the
   number of original observations (leaves) in the non-singleton
   cluster ``i``.

This function is useful when loading in linkages from legacy data
files generated by MATLAB.

Parameters
----------
Z : ndarray
    A linkage matrix generated by MATLAB(TM).

Returns
-------
ZS : ndarray
    A linkage matrix compatible with ``scipy.cluster.hierarchy``.

See Also
--------
linkage : for a description of what a linkage matrix is.
to_mlab_linkage : transform from SciPy to MATLAB format.

Examples
--------
>>> import numpy as np
>>> from scipy.cluster.hierarchy import ward, from_mlab_linkage

Given a linkage matrix in MATLAB format ``mZ``, we can use
`scipy.cluster.hierarchy.from_mlab_linkage` to import
it into SciPy format:

>>> mZ = np.array([[1, 2, 1], [4, 5, 1], [7, 8, 1],
...                [10, 11, 1], [3, 13, 1.29099445],
...                [6, 14, 1.29099445],
...                [9, 15, 1.29099445],
...                [12, 16, 1.29099445],
...                [17, 18, 5.77350269],
...                [19, 20, 5.77350269],
...                [21, 22,  8.16496581]])

>>> Z = from_mlab_linkage(mZ)
>>> Z
array([[  0.        ,   1.        ,   1.        ,   2.        ],
       [  3.        ,   4.        ,   1.        ,   2.        ],
       [  6.        ,   7.        ,   1.        ,   2.        ],
       [  9.        ,  10.        ,   1.        ,   2.        ],
       [  2.        ,  12.        ,   1.29099445,   3.        ],
       [  5.        ,  13.        ,   1.29099445,   3.        ],
       [  8.        ,  14.        ,   1.29099445,   3.        ],
       [ 11.        ,  15.        ,   1.29099445,   3.        ],
       [ 16.        ,  17.        ,   5.77350269,   6.        ],
       [ 18.        ,  19.        ,   5.77350269,   6.        ],
       [ 20.        ,  21.        ,   8.16496581,  12.        ]])

As expected, the linkage matrix ``Z`` returned includes an
additional column counting the number of original samples in
each cluster. Also, all cluster indices are reduced by 1
(MATLAB format uses 1-indexing, whereas SciPy uses 0-indexing).

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