openSTARS (version 1.0.0)

calc_attributes_edges: Calculate attributes of the edges.

Description

For each edge (i.e. stream segment) additional attributes (predictor variables) are derived based on given raster maps.

Usage

calc_attributes_edges(input_raster, stat, attr_name, round_dig = 2,
  clean = TRUE)

Arguments

input_raster

name or character vector of names of the raster map(s) to calculate attributes from.

stat

name or character vector giving the statistics to be calculated, must be one of: min, max, mean, percent.

attr_name

name or character vector of column names for the attribute(s) to be calculated. Attribute names must not be longer than 8 characters.

round_dig

integer; number of digits to round results to. Can be a vector of different values or just one value for all attributes.

clean

logical; should intermediate files be deleted

Value

Nothing. The function appends new columns to the 'edges' attribute table with column names given in attr_name. For each attribute, two columns are appended: one giving the attribute for the rca of the edge ("attribute_name_e") and one for the attribute of the total catchment of the edge ("attribute_name_c").

Details

First, the subcatchments for all edges are calculated. Then these are intersected with the given raster maps and the desired statistics are computed. This is needed to compute approximate attribute values for sites calc_attributes_sites_approx.

For stat = "percent" the input_raster must be coded as 1 and 0 (e.g., cells occupied by the land use under consideration and not). If the input_raster consists of percentages per cell (e.g., proportional land use of a certain type per cell) stat = "mean" gives the overall proportion of this land use.

Examples

# NOT RUN {
# Initiate GRASS session
if(.Platform$OS.type == "windows"){
  gisbase = "c:/Program Files/GRASS GIS 7.2.0"
  } else {
  gisbase = "/usr/lib/grass72/"
  }
initGRASS(gisBase = gisbase,
    home = tempdir(),
    override = TRUE)

# Load files into GRASS
dem_path <- system.file("extdata", "nc", "elev_ned_30m.tif", package = "openSTARS")
sites_path <- system.file("extdata", "nc", "sites_nc.shp", package = "openSTARS")
setup_grass_environment(dem = dem_path, sites = sites_path)
import_data(dem = dem_path, sites = sites_path)
gmeta()

# Derive streams from DEM
derive_streams(burn = 0, accum_threshold = 700, condition = TRUE, clean = TRUE)

# Check and correct complex junctions (there are no complex juctions in this 
# example date set)
cj <- check_compl_junctions()
if(cj){
  correct_compl_junctions()
}

# Prepare edges
calc_edges()

# Plot data
dem <- readRAST('dem', ignore.stderr = TRUE)
edges <- readVECT('edges', ignore.stderr = TRUE)
plot(dem, col = terrain.colors(20))
lines(edges, col = "blue", lwd = 2)
# }
# NOT RUN {
# }