libpysal.weights.w_symmetric_difference¶

libpysal.weights.w_symmetric_difference(w1, w2, w_shape='all', constrained=True, **kwargs)[source]¶

Returns a binary weights object, w, that includes only neighbor pairs that are not shared by w1 and w2. The w_shape and constrained parameters determine which pairs that are not shared by w1 and w2 are returned.

Parameters:¶

w1 : W¶

object

w2 : W¶

object

w_shape : string¶

Defines the shape of the returned weights matrix. ‘all’ returns a matrix with all the unique IDs from w1 and w2; and ‘min’ returns a matrix with the IDs not shared by w1 and w2.

constrained : boolean¶

If False then the full set of neighbor pairs that are not shared by w1 and w2 are returned. If True then those pairs that would not be possible if w_shape=’min’ are dropped. Ignored if w_shape is set to ‘min’.

**kwargs : keyword arguments¶

optional arguments for pysal.weights.W

Returns:¶

w – object

Return type:¶

W

Notes

ID comparisons are performed using ==, therefore the integer ID 2 is equivalent to the float ID 2.0.

Examples

Construct queen weights matrix for a 4x4 (16 areas) region (w1) and a rook matrix for a 6x4 (24 areas) region (w2). The symmetric difference of these two matrices (with w_shape set to ‘all’ and constrained set to False) contains the corner joins in the overlap area, all the joins in the non-overlap area.

>>> from libpysal.weights import lat2W, w_symmetric_difference
>>> w1 = lat2W(4,4,rook=False)
>>> w2 = lat2W(6,4,rook=True)
>>> w = w_symmetric_difference(w1, w2, constrained=False)
>>> w1[0] == w[0]
False
>>> w1.neighbors[15]
[10, 11, 14]
>>> w2.neighbors[15]
[11, 14, 19]
>>> set(w.neighbors[15]) == set([10, 19])
True