SpatialPosition (version 2.1.2)

isopoly: Create Spatial Polygons Contours from a Raster

Description

This function creates spatial polygons of contours from a raster.

Usage

isopoly(
  x,
  nclass = 8,
  breaks,
  mask,
  xcoords = "COORDX",
  ycoords = "COORDY",
  var = "OUTPUT",
  returnclass = "sp"
)

Value

The output is an sf POLYGON data.frame. The data frame contains four fields: id (id of each polygon), min and max (minimum and maximum breaks of the polygon), center (central values of classes).

Arguments

x

sf POINT data.frame; must contain X, Y and OUTPUT fields.

nclass

numeric; a number of class.

breaks

numeric; a vector of break values.

mask

sf POLYGON data.frame; mask used to clip contour shapes.

xcoords

character; name of the X coordinates field in x.

ycoords

character; name of the Y coordinates field in x.

var

character; name of the OUTPUT field in x.

returnclass

"sp" or "sf"; class of the returned object.

See Also

stewart.

Examples

data(hospital)
# Compute Stewart potentials
mystewart <- stewart(knownpts = hospital, varname = "capacity",
                     typefct = "exponential", span = 1000, beta = 3,
                     mask = paris, returnclass = "sf")
# Create contour
contourpoly <- isopoly(x = mystewart,
                       nclass = 6,
                       mask = paris, returnclass = "sf")
library(sf)
plot(st_geometry(contourpoly))
if(require(cartography)){
  # Created breaks
  bks <- sort(unique(c(contourpoly$min, contourpoly$max)))
  opar <- par(mar = c(0,0,1.2,0))
  # Display the map
  choroLayer(x = contourpoly,
             var = "center", legend.pos = "topleft",
             breaks = bks, border = "grey90",
             lwd = 0.2,
             legend.title.txt = "Potential number\nof beds in the\nneighbourhood",
             legend.values.rnd = 0)
  plot(st_geometry(paris), add = TRUE)
  propSymbolsLayer(x = hospital, var = "capacity",
                   legend.pos = "right",
                   legend.title.txt = "Number of beds",
                   col = "#ff000020")
  layoutLayer(title = "Global Accessibility to Public Hospitals",
              sources = "", author = "")
  par(opar)
}