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Great-circle origin-destination flow map

Source: R/map-symbols.R
flow_map.Rd

Draws great-circle arcs between country pairs from an origin-destination table (trade, migration, flights, remittances), resolving both endpoints to centroids automatically.

Usage

flow_map(
  data,
  from,
  to,
  weight = NULL,
  origin = "country.name",
  arc_points = 50,
  projection = "equal_earth",
  footnote = "auto",
  n = deprecated()
)

Arguments

data

An OD table.

from, to

The origin and destination country columns (unquoted; names or iso3c).

weight

Optional column controlling arc width/alpha (unquoted).

origin

How to read from/to (countrycode origin scheme).

arc_points

Points per arc (default 50): the smoothness of each great circle.

projection

Map projection, as in world_map() (default "equal_earth"). The arcs are great circles in any projection.

footnote

The caption: "auto" (default) says how many flows were drawn, a string is used as given, FALSE adds nothing.

n

[Deprecated] Use arc_points.

Value

A ggplot object.

Backend

The polygon backend draws it, in projection (Equal Earth by default), so it needs no sf.

Examples

# \donttest{
od <- data.frame(from = c("China", "Germany"),
                 to = c("United States", "France"),
                 value = c(500, 200))
flow_map(od, from, to, value)

# }