### Description

Plot a layer of colored and graduated links. Links are plotted according to discrete classes of widths. Colors depend on a discrete variable of categories.

### Usage

gradLinkTypoLayer(
x,
df,
xid = NULL,
dfid = NULL,
var,
breaks = getBreaks(v = df[, var], nclass = 4, method = "quantile"),
lwd = c(1, 2, 4, 6),
var2,
col = NULL,
colNA = "white",
legend.title.cex = 0.8,
legend.values.cex = 0.6,
legend.values.rnd = 0,
legend.var.pos = "bottomleft",
legend.var.title.txt = var,
legend.var.frame = FALSE,
legend.var2.pos = "topright",
legend.var2.title.txt = var2,
legend.var2.values.order = NULL,
legend.var2.nodata = "no data",
legend.var2.frame = FALSE,
)


### Arguments

 x an sf object, a simple feature collection. df a data frame that contains identifiers of starting and ending points and variables. xid names of the identifier variables in x, character vector of length 2, default to the 2 first columns. (optional) dfid names of the identifier variables in df, character vector of length 2, default to the two first columns. (optional) var name of the variable used to plot the links widths. breaks break values in sorted order to indicate the intervals for assigning the lines widths. lwd vector of widths (classes of widths). var2 name of the variable used to plot the links colors. col color of the links. colNA no data color. 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.var.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)). legend.var.title.txt title of the legend (numeric data). legend.var.frame whether to add a frame to the legend (TRUE) or not (FALSE). legend.var2.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)). legend.var2.title.txt title of the legend (factor data). legend.var2.values.order values order in the legend, a character vector that matches var modalities. Colors will be affected following this order. legend.var2.nodata text for "no data" values legend.var2.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).

### Note

Unlike most of cartography functions, identifiers variables are mandatory.

### Examples

library(sf)
# Create a link layer - work mobilities to Fort-de-France (97209) and
# Le Lamentin (97213)
mob.sf <- getLinkLayer(x = mtq, df = mob[mob\$j %in% c(97209, 97213),],
dfid = c("i", "j"))
# Plot the links - Work mobility
plot(st_geometry(mtq), col = "grey60",border = "grey20")