cartography (version 2.1.0)

discLayer: 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, spdf, spdfid1, spdfid2)

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

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

var

name of the numeric field in df used to compute and plot discontinuities.

method

a discretization 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).

spdf

defunct.

spdfid1

defunct.

spdfid2

defunct.

Value

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

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).

See Also

getBorders, gradLinkLayer, legendGradLines

Examples

# NOT RUN {
library(sp)
data(nuts2006)
# Get borders
nuts0.contig <- getBorders(x = nuts0.spdf)
# GDP per capita
nuts0.df$gdpcap <- nuts0.df$gdppps2008/nuts0.df$pop2008
# Plot countries
plot(nuts0.spdf, col="#CCCCCC", lwd=1, border="white")
# Plot discontinuities
discLayer(x = nuts0.contig, df = nuts0.df,
          var = "gdpcap", col="red", nclass=5,
          method="quantile", threshold = 0.5, sizemin = 1,
          sizemax = 10, type = "rel", legend.frame = TRUE,
          legend.title.txt = "GDP per Capita discontinuities\n(relative)",
          legend.pos = "topright", add=TRUE)

library(sf)
mtq <- st_read(system.file("shape/martinique.shp", package="cartography"))
# Get borders
mtq.borders <- getBorders(x = mtq)
# Employees share in the pop
mtq$emp_share <- 100 * mtq$C13_CS5/mtq$C13_POP
# Plot this share
choroLayer(x = mtq, var = "emp_share", border = NA, method = 'q6', 
           legend.values.rnd = 1, legend.pos = "topleft", 
           legend.title.txt = "Share of employees\nin the population\n(age > 15 y.o.)" )
# Plot discontinuities
discLayer(x = mtq.borders, df = mtq,
          var = "emp_share", col="darkorange2", nclass=3,
          method="quantile", threshold = 0.5, sizemin = 0.5,
          sizemax = 10, type = "abs", 
          legend.title.txt = "Discontinuities\n(absolute difference)",
          legend.pos = "bottomleft", add=TRUE)
# }