Syntax

   FACTORY_DEF <ReaderKeyword> DensityFactory
   [FACTORY_NAME <factory name>] 
   [INPUT (REQUESTOR|REFERENCE)
      FEATURE_TYPE <feature type>
      [<attribute name> <attribute value>]*
      [<feature function>]*]+
   DENS_TYPE (LINE_DENS|AREA_DENS|NUMBER_DENS)
   ATTR_NAME <field name>
   [GROUP_BY [<field name>]+]*
   [REJECT_INVALID_GEOM (Yes|No)]
   [VECTOR_ONLY (Yes|No)]
   [OUTPUT (REFERENCE|REQUESTOR)
      FEATURE_TYPE <feature type>
      [<attribute name> <attribute value>]*
      [<feature function>]*]*

Overview

   This factory is used for calculating the density of features based on a 
   reference area. For example we could calculate the density of all the rivers 
   in British Columbia (the requestor features) based on the area of British 
   Columbia (the reference feature).

   The input features may be grouped based on attribute values specified in the 
   GROUP_BY clause.

   The DENS_TYPE clause specifies which method we will use when calculating the 
   density. LINE_DENS is used when you would like to calculate the density based 
   on the length of the lines in each group of requestors. AREA_DENS is used 
   when you would like to calculate the density based on the total area of a 
   group of requestors. NUMBER_DENS is used when you want to calculate the 
   density based on the number of features in a group of requestors.

   The ATTR_NAME clause specifies what the name of the attribute will be that 
   holds the density which is calculated.

   The factory does not make any assumptions about whether or not objects used 
   as the REFERENCE are inside of the REQUESTOR feature. If this behavior is 
   what is desired then a SpatialRelator transformer can be used in conjunction.

   When REJECT_INVALID_PARAMS is Yes, the factory will output invalid features to
   Rejected port.
   
   When VECTOR_ONLY is set to Yes, only vector geometries (nulls/points/lines/areas)
   will contribute to the length and area modes.  Only collections containing a non-null
   vector, or exclusively containing nulls will be allowed.  Geometries will no longer 
   be rejected/discarded based on length, and will instead be discarded based on geometry
   type.

Input Tags

   The DensityFactory uses the following input tags.
   
   REFERENCE   
   
      All features which we want to use as a reference to calculate the density 
      are placed in this port.

   REQUESTOR   
   
      All features which we would like to calculate the density of are placed in 
      this port.

Output Tags

   The DensityFactory supports the following output tags.
   
   REFERENCE   
   
      All features which originally came through the REFERENCE port are placed 
      here.
   
   REQUESTOR   
   
      All features which originally came through the REQUESTOR port are placed 
      here.