stplanr (version 0.1.8)

od_aggregate: Aggregate OD data between polygon geometries

Description

Aggregate OD data between polygon geometries

Usage

od_aggregate(flow, zones, aggzones, cols = FALSE, aggcols = FALSE,
  FUN = sum, prop_by_area = ifelse(identical(FUN, mean) == FALSE, TRUE,
  FALSE), digits = getOption("digits"))

Arguments

flow

A data frame representing the flow between two points or zones. The first two columns of this data frame should correspond to the first column of the data in the zones. Thus in cents, the first column is geo_code. This corresponds to the first two columns of flow.

zones

A SpatialPolygonsDataFrame or SpatialPointsDataFrame representing the original centroids or boundaries of the travel flow data. Note that in the case of a SpatialPointsDataFrame, the entirety of the flow will be allocated to the polygon in which the point is located rather than being distributed by area.

aggzones

A SpatialPolygonsDataFrame containing the new boundaries to aggregate to.

cols

A character vector containing the names of columns on which to apply FUN. By default, all numeric columns are aggregated.

aggcols

A character vector containing the names of columns in aggzones to retain in the aggregated data.frame. By default, only the first column is retained. These columns are renamed with a prefix of "o_" and "d_".

FUN

Function to use on aggregation. Default is sum.

prop_by_area

Boolean value indicating if the values should be proportionally adjusted based on area. Default is TRUE unless FUN = mean.

digits

The number of digits to use when proportionally adjusting values based on area. Default is the value of getOption("digits").

Value

data.frame containing the aggregated od flows.

Details

Origin-destination ('OD') flow data is often provided in the form of 1 line per flow with zone codes of origin and destination centroids. This function aggregates OD flows between polygon geometries allocating the original flows to larger zones based on area.

Examples

# NOT RUN {
data(flow)
data(zones)
zones@data$region <- 1
zones@data[c(2, 5), c('region')] <- 2
aggzones <- SpatialPolygonsDataFrame(rgeos::gUnaryUnion(
 zones,
 id = zones@data$region), data.frame(region=c(1, 2))
)
zones@data$region <- NULL
od_aggregate(flow, zones, aggzones)
# another example with more zones and plots
zones$quadrant = quadrant(zones, number_out = TRUE)
aggzones <- SpatialPolygonsDataFrame(
rgeos::gUnaryUnion(
 zones,
 id = zones@data$quadrant), data.frame(region = c(1:4))
)
od = od_aggregate(flow, zones, aggzones)
od_sp = od2line(flow, zones)
zones@data = cbind(1:nrow(zones), zones@data)
od_sp_agg = od2line(od, zones, aggzones)
# plot results
plot(aggzones, lwd = 5)
plot(zones, border = "red", add = TRUE)
plot(od_sp, add = TRUE, col = "yellow")
lwd = od_sp_agg$All / 50
plot(od_sp_agg, lwd = lwd, add = TRUE)
# }