org.opentripplanner.analyst.batch

Class DecayAccumulator

java.lang.Object

org.opentripplanner.analyst.batch.DecayAccumulator

All Implemented Interfaces:

Accumulator

public class DecayAccumulator
extends Object
implements Accumulator

A simple exponential decay (gravity) model, as defined in, for example Geurs, Karst T, and Bert van Wee. "Accessibility Evaluation of Land-use and Transport Strategies: Review and Research Directions." Journal of Transport Geography 12, no. 2 (2004): 127–140. http://www.sciencedirect.com/science/article/pii/S0966692303000607, 133. The equation is A_i = \sum{D_j e^{-\Beta c_{ij}}}, where A_i is the accessibility at location i, D_j is the attractiveness of location j, \Beta is the cost sensitivity parameter, and c_{ij} is the cost of going from i to j (Geurs and Wee 2004, 133).

Field Summary

Fields

Modifier and Type	Field and Description
double	lambda This is the cost sensitivity parameter, the multiplier for the exponentiation of cost.

Constructor Summary

Constructors

Constructor and Description
DecayAccumulator()

Method Summary

Modifier and Type	Method and Description
void	accumulate(double amount, ResultSet current, ResultSet accumulated)
void	finish()
void	setHalfLifeMinutes(int halfLifeMinutes) This is a convenience function to set the cost sensitivity with more real-world values.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

lambda

public double lambda

This is the cost sensitivity parameter, the multiplier for the exponentiation of cost. See Geurs and Wee 2004, 133. (Note that Geurs and Wee 2004 call it beta, but it's the same variable)

Constructor Detail

DecayAccumulator

public DecayAccumulator()

Method Detail

setHalfLifeMinutes

public void setHalfLifeMinutes(int halfLifeMinutes)

This is a convenience function to set the cost sensitivity with more real-world values. The value passed in is multiplied by 60 and the reciprocal is taken.

Parameters:

halfLifeMinutes -

accumulate

public void accumulate(double amount,
                       ResultSet current,
                       ResultSet accumulated)

Specified by:

accumulate in interface Accumulator

finish

public void finish()

Specified by:

finish in interface Accumulator