Polarization

Display:

Description
The purpose of this module is to calculate the probability of attraction exerted by a pole (e.g. a large town), as a function of the weight attributed to it and the minimum distance separating the entities from the pole. The continuous data input represents the weights attributed to the poles.

The pole map can contain surfaces, lines and/or points.

Indirectly, this module enables two types of map to be obtained:
   - either maps of attraction gradients.
   - or polarization maps.

This means that the module can generate two types of data:
   - A continuous data output expressing the value of the potential of attraction.
   - A qualitative data output expressing the strongest center of attraction for each entity.

If you choose the qualitative data, then:
   - you can parametrize it in choosing the identifier, the name, or the expression identifier-name for each pole.
   - in the Result text area, you will find the number of elements associated to each pole.

Formula used:
Let:

• E be an entity on the working map
• P be an input pole, with weight M
• X be the exponent selected as a parameter

Then,     V = M  /  ( dist(E,P) ^ X  )                 (dist = distance  ,  ^ = raised to the power of )

The value given for E is the largest V among all the poles.

The distance given is calculated as the shortest distance between the centroid of the entity and the edge of the pole. However, if the Compute from centroids box has not been checked, it is the outline of the entity that is used.

Script:

2      module untyped_list ""
3        mod_type integer "103"
3        mod_subtype integer "508"
3        mod_name string "Polarisation"
3        mod_dads integer_list ""
4          ? integer "3"
4          ? integer "6"
3        exponent double "2"
3        output_type integer "10"
3        take_centroid boolean "T"
3        output_id boolean "F"
3        output_name boolean "T"
3        output_id_name boolean "F"
3        poles_tree untyped_list ""
4          pole untyped_list ""
5            pole_id string "Tours"
5            pole_elem_nb integer "254"
4          pole untyped_list ""
5            pole_id string "Chinon"
5            pole_elem_nb integer "13"
4          pole untyped_list ""
5            pole_id string "Loches"
5            pole_elem_nb integer "10"

Values for output_type:
Continuous    2
Qualitative  10