*! version 1.0.2 28feb2014
help spmat contiguity

Title

spmat contiguity -- Create an spmat object containing a
contiguity matrix W

Syntax

spmat contiguity objname
[if] [in] using filename, id(varname) [options]

* id(varname) ID variable

rook rook contiguity

normalize(norm) normalization method

tolerance(#) numerical tolerance

banded banded storage

replace replace objname

saving(filename, ...) save neighbor info to a text file

nomatrix do not create objname

* Required

Description

spmat contiguity puts a contiguity matrix W into the new
spmat object objname. The ijth element of W
is 1 if points i and j are neighbors and is 0 otherwise.

spmat contiguity uses both the dataset in memory and a dataset
containing the coordinates of polygons. The coordinates dataset must be
in the format created by shp2dta or mif2dta.

Options

id(varname)
specifies a numeric variable that contains a unique identifier for each
observation. This option is required.

rook specifies that only points that share a common edge should
be considered neighbors (rook contiguity). The default is to
include points that share a common vertex (queen contiguity).
Rook contiguity is computationally more difficult than queen contiguity.

normalize(norm) specifies the normalization method.
norm can be row, minmax, or
spectral.

tolerance(#) specifies the numerical tolerance used in deciding
whether two places are rook or queen neighbors. The default is
tolerance(1e-7).

banded instructs spmat to store the contiguity matrix in
a banded form; see Remarks in spmat tobanded
for details.

replace allows objname to be overwritten if it already exists.

saving(filename [, replace]) requests that
the matrix be written to filename in the neighbor-list format.
The first line of the file contains the total number
of places and, if the matrix is banded, the lower and upper band.
Each remaining line lists a place ID followed by its
neighbors, if any. replace allows filename
to be overwritten if it already exists.

nomatrix specifies that the spmat object objname and
spatial-weighting matrix W not be created. In conjunction with
saving(), this option allows for creating a text file containing
a neighbor list without constructing the underlying contiguity matrix.

Example

Setup

. clear all

. set memory 50m

. use pollute

Create the spmat object cobj containing a minmax-normalized contiguity matrix

. spmat contiguity cobj using pollutexy, id(id) normalize(minmax)

Also see

Online: spmat, spreg, spivreg,
spmap, shp2dta, mif2dta (if installed)