Origin-destination small multiples

One small map per origin, each showing where that origin's flow goes. The answer to the arc map's central problem: past a few dozen flows, flow_map() is a plate of spaghetti and an OD map is legible.

Usage

od_map(
  data,
  from,
  to,
  weight = NULL,
  origin = "country.name",
  origins = 6,
  direction = c("out", "in"),
  ...
)

Arguments

data

An OD table.

from, to

The origin and destination country columns (unquoted).

weight

The flow column (unquoted). If omitted, every pair counts as 1.

origin

How to read from/to (default "country.name").

origins

Which origins to draw. A character vector of names or codes, or an integer giving how many of the largest to take (default 6).

Note that this is not origin, which it sits next to: origin is the coding scheme from/to are written in, origins is which of them to put on the page. Confusing the two is diagnosed rather than left to fail further in.

direction

"out" (default; one panel per origin, showing destinations) or "in" (one panel per destination, showing origins).

...

Passed to world_map().

Value

A faceted ggplot object.

See also

flow_map(), country_network(), facet_map()

Examples

# \donttest{
od <- data.frame(
  from = rep(c("China", "Germany", "USA"), each = 3),
  to   = c("USA", "Japan", "Brazil", "France", "Italy", "Poland",
           "Mexico", "Canada", "Japan"),
  value = c(500, 200, 90, 80, 70, 60, 300, 280, 120)
)
if (requireNamespace("maps", quietly = TRUE)) {
  od_map(od, from, to, value, origins = 3)
}

# }