ttwa (version 0.8.5.1)

ttwa: Zoning Commuting flow

Description

This function computes the commuting areas from a flow data. It is especially effective for calculating the travel to work area (TTWA). TTWA are defined to reflect areas where the bulk of the resident population also works within the same area. TTWA defines local labour market area. The ttwa function uses a greedy algorithm. Progressively, areas aggregate themselves with their link when above a threshold. The ttwa is an adaptation of the algorithm used by the INSEE zoning, Anabel.

Usage

ttwa(df, origin, destination, flow, conti = NULL, 
minimum_link = 0.00001, size_center, list_center = NULL)

Arguments

df

data frame that contains the flow information

origin

name of the variable that containd the identifier of the origin area

destination

name of the variable that containd the identifier of the destination area

flow

name of the qualitative variable that contains the flow

conti

default NULL, name of the boolean variable that contains the contiguity beetween origin and destination area

minimum_link

minimum link aggregation allows between area

size_center

size of area who can't be aggregated to an other area. enter_size determines the minimum size of commuting area.

list_center

list of identifiers of non-aggregatable territories to other centers but they can attract other territories and become centers or otherwise isolated clusters.

Value

An object of class "zoning" is a list containing at least the following components:

zoning

data frame contains the initial area and their commuting area of attachment

log

data frame containing the log of the greedy processus

data

data frame containing the aggregated flow between commuting area

statistic

data frame containing the statistics area by zone (the total outflow, rate stable at origin, number of primary territories)

Details

The ttwa is an adaptation of the algorithm used by the INSEE zoning, Anabel. For each iteration, we search for the strongest link between the two areas which meet the parameters of aggregation (contiguity and center size). Then, it is aggregated to the lines of the data.frame associated with the two areas. Thus, the area's name formed is the name of the destination area of the stream. It repeats the process until we can find areas with a sufficient nexus. The link between area i to j is defined as $flow_ij/total_outflow_i$. The constraint of contiguity provides a related zoning. It may be appropriated to add zeros to the flow variable between contiguous areas without flow to allow the construction of aggregation areas. Quality zoning is measured by the rate of steady flow in commuting area.

References

Christophe Terrier web site is a reference to the method Anabel-Mirabel: www.christophe-terrier.com

See Also

reunion_ttw

Examples

data(reunion_ttw) #commuting flow in Reunion island
zone_emploi<-ttwa(df=reunion_ttw,origin="HOME",
  destination="WORK", flow="FLOW",
  conti="CONTI",size_center=50000)
zone_emploi$statistic #Zoning quality 
# 4 centers : Saint-Denis, Saint-Paul, Saint-Pierre and Saint-Benoit
center_emploi<-ttwa(df=reunion_ttw,origin="HOME",
  destination="WORK",flow="FLOW",
  conti="CONTI",size_center=500000,
  list_center=c("97411","97415","97416","97410"))
center_emploi$statistic