The Geographic Identifier variables give us information about the geographies we are using in our analysis. Figures such as the Area (square miles or square kilometers), or Centroid coordinates (Latitude and Longitude of an area's geographic center) of the selected geography can be attached as data variables to our output.
Additionally, the user can also choose to output geography names and keys within their selected geographies. Allocate can easily determine what geographies contain other geographies and give the user an accurate answer, again attaching the data variables to the selected output.
When geographies are not a one to one relationship, meaning there may be polygons that partially occupy more than one Geographic Identifier geography, Allocate will utilize an actual area weighted method for determining which area to assign a polygon to. A polygon object must overlap at least half of its total coverage by a Geographic Identifier polygon to be assigned that Geographic Identifier ID. Additionally if multiple Geographic Identifier IDs are assigned, the record will be flagged with *.
GeoID demoX files are special demox files for producing Geographic identifiers. They use an actual area weighted method for determining which area to assign a polygon to. It is typically used to assign a ZIP code or county code to a geography for an Allocate report.
This demoX file requires a YXDB file that has the polygons along with the fields that you want to apply as GeoIdentifiers. It is highly recommended that the YXDB file be sorted on the SpatialObject and also to not have any extra fields for maximum performance.
GeoIdentifiers have been built to offer users the ability to control how a geography assignment is made. Users can set the minimum overlap that must exist in order for a geography assignment to be made (no less than 50%). In addition the value for marking an assignment as a multiple match is controllable as is the symbol identifier for multiple match.
There are 3 special parameters that can be modified:
assignThreshold
This is a number from 50 to 99.9 that sets the minimum overlap that must exist to assign a GeoID to a Allocate Geography. If set to 50, that means a radius (or other geography) must be at least 50% covered by a GeoID polygon (like a ZIP code) to be assigned that GeoID. The default is 50.
singleAssignThreshold
This is a number fromassignThresholdto 100 that determines if a GeoID is marked as a multiple. The default is 90.
In addition, there is one special field: [CoverageArea]. If this field is used as the source field name, it is not required to be in the YXDB file and it will output a numeric value for the exact amount of coverage for the selected GeoID.
Here is a example of the raw XML of a DemoX file. It is presuming that you have ZIP.yxdb in the same directory.
<?xml version="1.0" encoding="ISO-8859-1" standalone="no" ?>
<DemoX type="GeoID">
<DemoFileInfo copyright="(C) 2010lteryx, Inc" name="ZIP GeoID" version="2010>
<DataConnectionString>ZIP.yxdb</DataConnectionString>
<Multiple assignThreshold="50" singleAssignThreshold="90" multipleDesignator="*" />
<VariableList>
<Category name="ZIP GeoID">
<Vintage name="Current Year" year="2010">
<Variable description="ZIP Name" fieldName="ZIP_Name" fieldNameLong="" isIndexable="False" sourceFieldName="Name" units="String"/>
<Variable description="ZIP Key" fieldName="ZIP_Key" fieldNameLong="" isIndexable="False" sourceFieldName="Key" units="String"/>
<Variable description="ZIP Area" fieldName="ZIP_Area" fieldNameLong="" isIndexable="False" sourceFieldName="AreaSqMi" units="Physical"/>
<Variable description="ZIP Coverage Area" fieldName="ZIP__Coverage_Area" fieldNameLong="" isIndexable="False" sourceFieldName="[CoverageArea]" units="Percent"/>
</Vintage>
</Category>
</VariableList>
</DemoX>
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