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Gravity Model Macro

The Gravity Model Macro is an iterative macro that takes each demand-pull and associates a particular Gravity Value to it based on the given supply to produce a Gravity for each Demand ID and create the demand surface. You can specify a minimum relevant distance, frictional movement exponent, and Null Competitor Distance. You can also select to Filter on Demand Farther than 2x Null competitor distance, choose to use a Null Competitor, or return the full detail of the iterative values.

For more information on the Gravity Model, go to Gravity Model.

Configure the Tool

  1. The Gravity Model takes 2 Inputs on 2 Tabs:

    • In-Demand Locations: These are your potential locations. Use the dropdowns to select...

      • Demand Location ID: A unique identifier per record.

      • Demand: The demand value each record is assigned.

      • Spatial Object: The physical point of the location.

    • In-Fixed Locations: These are your existing locations. Use the dropdowns to select:

      • Supply ID: A unique identifier per record.

      • Spatial Object: The physical point of the location.

  2. Gravity Model Tab:

    • Minimum Relevant Distance: This parameter provides for the fact that attraction is not inversely proportional to distance at close proximity. For example, if a customer lives within one block of two similar convenience stores, distance is not relevant to the customer's decision (minimum relevant distance ~ 0.1 miles). Likewise, a person looking for a luxury car might not even consider the distance to the dealership unless one location is 5 miles or further from the other (minimum relevant distance ~ 5 miles).

      The default is 0.50.

    • Friction of Movement (Exponent): The effect of distance on the interaction between origin and destination zones. Friction of Movement parameters includes terms of cost, time spent on commuting between origin and destination zones, multidimensional measures combining time, money, and effort spent in commuting between zones, (b) the values of the exponent of the distance function, also known as the "distance decay parameter" – which varies with the purpose of the interaction (for example, trip purpose) as well as with distance itself and (c) the use of other functional forms of the distance function.

      The default is 2.0.

    • Null Competitor Distance: The distance at which most locations (fixed, potential, and competitor) see business decline substantially. In general, this can be thought of as the distance at which 50% of customers decide on other means to fulfill their objective. If the store is X miles away, they might buy through mail order, purchase online, or buy an alternative product.

      The default is 15.

    • Options:

      • Filter Demand Farther than 2x Null Competitor Distance

      • Use Null Competitor: When checked, this tool puts an imaginary competitor that is many miles away from every demand centroid.

      • Return Full Detail: When checked, all of the data points, IDs, and gravity are returned. If unchecked, only the Demand ID and the gravity is returned.