Simple Agents, Complex Emergent City: Agent-Based Modeling of Intraurban Migration - Computational Approaches for Urban Environments - page 123

Randomly select a homebuyer B i

Calculate P ij i.e., the possibility of B i

buying vacant house H i in S vh

Potential
Homebuyers

Vacant
Houses
{

Generate a random number P ir

}

{ }

S = B , i = 1 2 ... S = H , j = 1 2 ...

ph i

vh j

Find in H t S vh . Its probability P it ≥ P ir

and P it -P ir ≤ P ij -P ir , j=1,2,.., n, j≠t

No

Yes

H t exists?

Remove B i Add H i , Remove H t

Update Context

Export the migration origin and destination data

Fig. 6.1 Modeled intraurban migration process

where is the mean direction, is a measure of variance of directions around
,and I 0 () is a modified Bessel function with order zero. When is zero, the
distribution is uniformly circular (i.e., with equal probability in any direction); when
it is larger, the distribution will concentrate around in a similar fashion to the
normal distribution.
We bring together these sociospatial findings on housing perception via a
conceptual agent-based model of the distance and directional relationships among
housing vacancies and current dwellings of potential migrants (Fig. 6.1 ). This model
adopts two housing search and relocation strategies—distance-only and distance-
plus-direction—that condition intervening opportunity theory with the statistical
distribution of moving distances and directions as specified by the negative expo-
nential and von Mises distributions (after Clark et al. 2003 ). The model is based on
two lists for the regional housing market: one of potential homebuyers and another
of vacant houses. Each model year, the model iterates over homebuyers randomly.
Each homebuyer generates a random number and the vacant house with the closest
greater probability is chosen as the destination. When a homebuyer moves, he or
she is removed from the buyer list and the vacated house is added into the vacant
house list.