help spmat contiguity
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Title

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


Syntax

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


    options                       Description
    -------------------------------------------------------------------------
    * 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 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)