cartography (version 1.3.0)

discLayer: Discontinuities Layer

Description

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

Usage

discLayer(spdf, df, spdfid1 = NULL, spdfid2 = NULL, dfid = NULL, var, method = "quantile", nclass = NULL, 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

spdf

a SpatialLinesDataFrame, as outputed by the getBorders function.

df

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

spdfid1

first identifier of the border, default to the second column of the spdf data frame. (optional)

spdfid2

second identifier of the border, default to the third column of the spdf data frame. (optional)

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", "jenks","q6" or "geom" (see discretization Details).

nclass

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

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", "left", "right", "bottomleft", "bottom", "bottomright". 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).

Value

An invisible (invisible) SpatialLinesDataFrame 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

data(nuts2006)
# Get borders
nuts0.contig.spdf <- getBorders(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(spdf = nuts0.contig.spdf, 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)