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FAQ: What is the format of the Spatial Weights Matrix?

Question

What is the format of the Spatial Weights Matrix?

Answer

If the ArcGIS Desktop 9.0 Service Pack 1 AND the ArcGIS Desktop 9.0 Spatial Statistics QFE download have not been obtained, the format of the spatial weights matrix file is just as described in the geoprocessing help documentation -- in the ArcGIS Desktop help system see Geoprocessing > Geoprocessing Tool Reference > Spatial Statistics Toolbox > "Modeling spatial relationships". However, it is highly recommended that users download and install both. The reasons for this are outlined on the ArcGIS Desktop 9.0 Spatial Statistics QFE Web page. The links are provided in the Related Information section below.

After both of these items have been downloaded and installed, the format of the spatial weights matrix file is different from what is described in the help documentation.

The file must now have a header indicating which field is the Unique ID field. For both the 'Hot Spot Analysis' and 'Cluster and Outlier' tools, the FID cannot be used. If the FID must be used, calculate it to a different field, and use that field.

The format is as follows:

Unique Field Name
From_ID To_ID Weight
From_ID To_ID Weight
From_ID To_ID Weight
and so forth.

If the unique field name is "My_Unq_Fld" then the file appears as follows:

My_Unq_Fld
0 1 500
0 2 304
0 3 450
1 0 475
1 2 325
1 3 350
and so forth.

Related Information