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

Description Usage Arguments Details Examples

View source: R/catchmentArea.R

Description

Calculate catchment area and associated summary statistics using network.

Usage

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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 partly or entirely within the catchment area will be included in the returned SpatialPolygonsDataFrame but will not be adjusted for the proportion within the catchment area.

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 be converted to the projection used by the polygonlayer. In all cases the resulting object will be reprojected to the original coordinate system and projection of the polygon layer. Default is an Albers Equal Area projection but for more reliable results should use a local projection (e.g., Australian Albers Equal Area project).

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

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## Not run: 
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
)

## End(Not run)

stplanr documentation built on Oct. 20, 2018, 5:05 p.m.