stplanr (version 0.1.0)

calc_network_catchment: Calculate catchment area and associated summary statistics using network.

Description

Calculate catchment area and associated summary statistics using network.

Usage

calc_network_catchment(sln, polygonlayer, targetlayer, calccols,
  maximpedance = 1000, distance = 100,
  projection = paste0("+proj=aea +lat_1=90 +lat_2=-18.416667",
  " +lat_0=0 +lon_0=10 +x_0=0 +y_0=0",
  " +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"),
  retainAreaProportion = FALSE, dissolve = FALSE)

Arguments

sln

The SpatialLinesNetwork to use.

polygonlayer

A SpatialPolygonsDataFrame containing zones from which the summary statistics for the catchment variable will be calculated. Smaller polygons will increase the accuracy of the results.

targetlayer

A SpatialPolygonsDataFrame, SpatialLinesDataFrame or SpatialPointsDataFrame object containing the specifications of the facilities and zones for which the catchment areas are being calculated.

calccols

A vector of column names containing the variables in the polygonlayer to be used in the calculation of the summary statistics for the catchment area. If dissolve = FALSE, all other variables in the original SpatialPolygonsDataFrame for zones that fall par

maximpedance

The maximum value of the network's weight attribute in the units of the weight (default = 1000).

distance

Defines the additional catchment area around the network in the units of the projection. (default = 100 metres)

projection

The proj4string used to define the projection to be used for calculating the catchment areas or a character string 'austalbers' to use the Australian Albers Equal Area projection. Ignored if the polygonlayer is projected in which case the targetlayer will

retainAreaProportion

Boolean value. If TRUE retains a variable in the resulting SpatialPolygonsDataFrame containing the proportion of the original area within the catchment area (Default = FALSE).

dissolve

Boolean value. If TRUE collapses the underlying zones within the catchment area into a single region with statistics for the whole catchment area.

Details

Calculates the catchment area of a facility (e.g., cycle path) using network distance (or other weight variable) as well as summary statistics from variables available in a SpatialPolygonsDataFrame with census tracts or other zones. Assumes that the frequency of the variable is evenly distributed throughout the zone. Returns a SpatialPolygonsDataFrame.

Examples

data_dir <- system.file("extdata", package = "stplanr")
unzip(file.path(data_dir, 'smallsa1.zip'), exdir=tempdir())
unzip(file.path(data_dir, 'testcycleway.zip'), exdir=tempdir())
unzip(file.path(data_dir, 'sydroads.zip'), exdir=tempdir())
sa1income <- readOGR(tempdir(),"smallsa1")
testcycleway <- readOGR(tempdir(),"testcycleway")
sydroads <- readOGR(tempdir(),"roads")
sydnetwork <- SpatialLinesNetwork(sydroads)
calc_network_catchment(
   sln = sydnetwork,
   polygonlayer = sa1income,
   targetlayer = testcycleway,
   calccols = c('Total'),
   maximpedance = 800
   distance = 200,
   projection = 'austalbers',
   dissolve = TRUE
)