weights.spatial_lag — Spatial lag operators PySAL: Python Spatial Analysis Library

The weights.spatial_lag Spatial lag operators for PySAL

New in version 1.0.

spatial lag operations

pysal.weights.spatial_lag.lag_spatial(w, y)

Spatial lag operator. If w is row standardized, returns the average of each observation’s neighbors; if not, returns the weighted sum of each observation’s neighbors.

Parameters:

w : W

weights object

y : array

variable to take the lag of (note: assumed that the order of y matches w.id_order)

Returns:

wy : array

array of numeric values for the spatial lag

Examples

>>> import pysal
>>> neighbors={'c': ['b'], 'b': ['c', 'a'], 'a': ['b']}
>>> weights ={'c': [1.0], 'b': [1.0, 1.0], 'a': [1.0]}
>>> id_order=['a','b','c']
>>> w=pysal.W(neighbors,weights,id_order)
>>> y = np.array([0,1,2])
>>> lag_spatial(w,y)
array([ 1.,  2.,  1.])
>>> w.id_order=['b','c','a']
>>> y = np.array([1,2,0])
>>> lag_spatial(w,y)
array([ 2.,  1.,  1.])
>>> w=pysal.lat2W(3,3)
>>> y=np.arange(9)
>>> yl=lag_spatial(w,y)
>>> yl
array([  4.,   6.,   6.,  10.,  16.,  14.,  10.,  18.,  12.])
>>> w.transform='r'
>>> yl=lag_spatial(w,y)
>>> yl
array([ 2.        ,  2.        ,  3.        ,  3.33333333,  4.        ,
        4.66666667,  5.        ,  6.        ,  6.        ])
>>> w.transform='b'
>>> yl=lag_spatial(w,y)
>>> yl
array([  4.,   6.,   6.,  10.,  16.,  14.,  10.,  18.,  12.])
>>>