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Great-circle distance between islands

Source: R/distance.R
island_distance.Rd

Haversine (great-circle) distance between the coordinates of islands and territories, resolved from country names or ISO codes via the same matching as the rest of the package (see is_sids). A natural primitive for connectivity and isolation work on small islands.

Usage

island_distance(
  x,
  y = NULL,
  which = c("point", "capital"),
  unit = c("km", "mi", "nmi")
)

Arguments

x

A character vector of ISO codes or country names.

y

Optional second character vector. If NULL (the default) a full symmetric distance matrix among the elements of x is returned. If supplied, distances are computed element-wise between x and y, recycling the shorter of the two, so a single origin against many destinations gives the distance from that origin to each.

which

Coordinate to use: "point" (representative landmass point, the default) or "capital" (capital city).

unit

Output unit: "km" (kilometres, the default), "mi" (statute miles), or "nmi" (nautical miles).

Value

When y is NULL, a numeric matrix (length(x) by length(x)) with iso_code dimnames. Otherwise a named numeric vector. Unresolved inputs and territories without the requested coordinate propagate as NA.

See also

island_coords

Examples

# Spread of the Dutch Caribbean (ABC + SSS), in km
round(island_distance(c("AW", "CW", "BQ-BO", "SX", "BQ-SA", "BQ-SE")))
#>        AW  CW BQ-BO  SX BQ-SA BQ-SE
#> AW      0 122   191 962   920   933
#> CW    122   0    73 908   863   873
#> BQ-BO 191  73     0 856   811   818
#> SX    962 908   856   0    49    62
#> BQ-SA 920 863   811  49     0    32
#> BQ-SE 933 873   818  62    32     0

# One origin to many
island_distance("Aruba", c("Curacao", "Bonaire", "Sint Maarten"))
#>       CW    BQ-BO       SX 
#> 121.5695 190.7913 961.7026 

# Capital-to-capital, in nautical miles
island_distance("AW", "CW", which = "capital", unit = "nmi")
#>       CW 
#> 71.96274