discLayer {cartography}

Discontinuities Layer

Description

This function computes and plots spatial discontinuities. The discontinuities are plotted over the layer outputted by the getBorders function. The line widths reflect the ratio or the difference between values of an indicator in two neighbouring units.

Usage

discLayer(
  x,
  df,
  dfid = NULL,
  var,
  method = "quantile",
  nclass = 4,
  threshold = 0.75,
  type = "rel",
  sizemin = 1,
  sizemax = 10,
  col = "red",
  legend.pos = "bottomleft",
  legend.title.txt = "legend title",
  legend.title.cex = 0.8,
  legend.values.cex = 0.6,
  legend.values.rnd = 2,
  legend.frame = FALSE,
  add = TRUE
)

Arguments

x

an sf object, a simple feature collection, as outputted by the getBorders function.

df

a data frame that contains the values used to compute and plot discontinuities.

dfid

name of the identifier variable in df, default to the first column of df. (optional)

var

name of the numeric variable used to compute and plot discontinuities.

method

a classification method; one of "sd", "equal", "quantile", "fisher-jenks"," q6", "geom", "arith", "em" or "msd" (see getBreaks).

nclass

a targeted number of classes. If null, the number of class is automatically defined (see getBreaks).

threshold

share of represented borders, value between 0 (nothing) and 1 (all the discontinuities).

type

type of discontinuity measure, one of "rel" or "abs" (see Details).

sizemin

thickness of the smallest line.

sizemax

thickness of the biggest line.

col

color of the discontinuities lines.

legend.pos

position of the legend, one of "topleft", "top", "topright", "right", "bottomright", "bottom", "bottomleft", "left" or a vector of two coordinates in map units (c(x, y)). If legend.pos is "n" then the legend is not plotted.

legend.title.txt

title of the legend.

legend.title.cex

size of the legend title.

legend.values.cex

size of the values in the legend.

legend.values.rnd

number of decimal places of the values in the legend.

legend.frame

whether to add a frame to the legend (TRUE) or not (FALSE).

add

whether to add the layer to an existing plot (TRUE) or not (FALSE).

Details

The "rel" type of discontinuity is the result of pmax(value unit 1 / value unit 2, value unit 2 / value unit 1).
The "abs" type of discontinuity is the result of pmax(value unit 1 - value unit 2, value unit 2 - value unit 1).

Value

An invisible sf object (MULTISTRING) with the discontinuity measures is returned.

See Also

getBorders, gradLinkLayer, legendGradLines

Examples

library(sf)
mtq <- st_read(system.file("gpkg/mtq.gpkg", package="cartography"))
# Get borders
mtq.borders <- getBorders(x = mtq)
# Median Income 
choroLayer(x = mtq, var = "MED", border = "grey", lwd = 0.5, 
           method = 'equal', nclass = 6, legend.pos = "topleft",
           legend.title.txt = "Median Income\n(in euros)" )
# Discontinuities
discLayer(x = mtq.borders, df = mtq,
          var = "MED", col="red4", nclass=3,
          method="equal", threshold = 0.4, sizemin = 0.5,
          sizemax = 10, type = "abs",legend.values.rnd = 0,
          legend.title.txt = "Discontinuities\n(absolute difference)",
          legend.pos = "bottomleft", add=TRUE)