The COUNTREG Procedure

For a spatial lag of X model , the SPATIALID statement specifies a variable that identifies a spatial unit for each observation in the two data sets that are provided by the DATA= and WMAT= options in the PROC COUNTREG statement. The variable also identifies the rows and columns of the WMAT= data set. The values of the spatial ID variable cannot be missing in either the DATA= data set or the WMAT= data set. When there are multiple SPATIALID statements, the first SPATIALID statement takes precedence over others that follow. In such a circumstance, the first SPATIALID statement applies to all spatial lag of X models.

The variable in the SPATIALID statement can be either numeric or character. However, the type of spatial ID variable in both the primary data set (specified in the DATA= option) and the spatial weights data set (specified in the WMAT= option) must be the same. When the spatial ID variable is numeric, its value needs to be an integer. If you specify a number that is not an integer, PROC COUNTREG uses the integer part of that number for matching. When the variable is numeric, the first letter of column names in the WMAT= data set (which specifies a spatial unit) is discarded because a valid SAS variable name must start with a letter or an underscore. When a numeric column name (such as, 11) is in the WMAT= data set, the IMPORT procedure (in Base SAS) appends an underscore to the column name in order to make it a valid name (for example, 11 becomes _11).