stplanr (version 0.1.8)

onewaygeo: Aggregate flows so they become non-directional (by geometry - the slow way)

Description

Flow data often contains movement in two directions: from point A to point B and then from B to A. This can be problematic for transport planning, because the magnitude of flow along a route can be masked by flows the other direction. If only the largest flow in either direction is captured in an analysis, for example, the true extent of travel will by heavily under-estimated for OD pairs which have similar amounts of travel in both directions. Flows in both direction are often represented by overlapping lines with identical geometries (see flowlines) which can be confusing for users and are difficult to plot.

Usage

onewaygeo(x, attrib)

Arguments

x

A SpatialLinesDataFrame

attrib

A text string containing the name of the line's attribute to aggregate or a numeric vector of the columns to be aggregated

Value

onewaygeo outputs a SpatialLinesDataFrame with single lines and user-selected attribute values that have been aggregated. Only lines with a distance (i.e. not intra-zone flows) are included

Details

This function aggregates directional flows into non-directional flows, potentially halving the number of lines objects and reducing the number of overlapping lines to zero.

Examples

# NOT RUN {
data(flowlines)
plot(flowlines)
singlelines <- onewaygeo(flowlines, attrib = 3:14)
plot(singlelines, lwd = 3, col = "red")
lines(singlelines) # check we've got the right lines
sum(singlelines$All)
nrow(singlelines)
# }