weights.Wsets — Set operations on spatial weights

The weights.user module provides for set operations on weights objects .. versionadded:: 1.0

Set-like manipulation of weights matrices.

pysal.weights.Wsets.w_difference(w1, w2, w_shape='w1', constrained=True)

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

Parameters:

w1 : W object

w2 : W object

w_shape : string

Defines the shape of the returned weights matrix. ‘w1’ returns a matrix with the same IDs as w1; ‘all’ returns a matrix with all the unique IDs from w1 and w2; and ‘min’ returns a matrix with the IDs occurring in w1 and not in w2.

constrained : boolean

If False then the full set of neighbor pairs in w1 that are not in 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’.

Returns:

w : W object

Notes

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

Examples

>>> import pysal
>>> w1 = pysal.lat2W(4,4,rook=False)
>>> w2 = pysal.lat2W(4,4,rook=True)
>>> w = w_difference(w1, w2, constrained=False)
>>> w1[0] == w[0]
False
>>> w1.neighbors[15]
[10, 11, 14]
>>> w2.neighbors[15]
[11, 14]
>>> w.neighbors[15]
[10]
>>>

pysal.weights.Wsets.w_intersection(w1, w2, w_shape='w1')

Returns a binary weights object, w, that includes only those neighbor pairs that exist in both w1 and w2.

Parameters:

w1 : W object

w2 : W object

w_shape : string

Defines the shape of the returned weights matrix. ‘w1’ returns a matrix with the same IDs as w1; ‘all’ returns a matrix with all the unique IDs from w1 and w2; and ‘min’ returns a matrix with only the IDs occurring in both w1 and w2.

Returns:

w : W object

Notes

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

Examples

>>> import pysal
>>> w1 = pysal.lat2W(4,4)
>>> w2 = pysal.lat2W(6,4)
>>> w = w_intersection(w1, w2)
>>> w1[0] == w[0]
True
>>> w1.neighbors[15]
[11, 14]
>>> w2.neighbors[15]
[11, 14, 19]
>>> w.neighbors[15]
[11, 14]
>>>

pysal.weights.Wsets.w_subset(w1, ids)

Returns a binary weights object, w, that includes only those observations in ids.

Parameters:

w1 : W object

ids : list

A list containing the IDs to be include in the returned weights object.

Returns:

w : W object

Examples

>>> import pysal
>>> w1 = pysal.lat2W(6,4)
>>> ids = range(16)
>>> w = w_subset(w1, ids)
>>> w1[0] == w[0]
True
>>> w1.neighbors[15]
[11, 14, 19]
>>> w.neighbors[15]
[11, 14]
>>>

pysal.weights.Wsets.w_symmetric_difference(w1, w2, w_shape='all', constrained=True)

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’.

Returns:

w : W object

Notes

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

Examples

>>> import pysal
>>> w1 = pysal.lat2W(4,4,rook=False)
>>> w2 = pysal.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]
>>> w.neighbors[15]
[10, 19]
>>>

pysal.weights.Wsets.w_union(w1, w2)

Returns a binary weights object, w, that includes all neighbor pairs that exist in either w1 or w2.

Parameters:

w1 : W object

w2 : W object

Returns:

w : W object

Notes

ID comparisons are performed using ==, therefore the integer ID 2 is equivalent to the float ID 2.0. Returns a matrix with all the unique IDs from w1 and w2.

Examples

>>> import pysal
>>> w1 = pysal.lat2W(4,4)
>>> w2 = pysal.lat2W(6,4)
>>> w = w_union(w1, w2)
>>> w1[0] == w[0]
True
>>> w1.neighbors[15]
[11, 14]
>>> w2.neighbors[15]
[11, 14, 19]
>>> w.neighbors[15]
[19, 11, 14]
>>>