poi_multi: Pole of Inaccessibility for Multi-Polygons

In polylabelr: Find the Pole of Inaccessibility (Visual Center) of a Polygon

Pole of Inaccessibility for Multi-Polygons

Description

This function is a convenience function to be used with multi-polygons (lists of polygons). The function simply calls poi() for each polygon in the list and returns the point wit the maximum distance to the boundaries of the enclosing polygon.

Usage

poi_multi(polygons, ...)

Arguments

polygons	a list, each element containing entries x and y. See poi() for details about what these need to be.
...	Arguments passed on to poi x a vector of x coordinates or a matrix or data.frame of x and y coordinates, a list of components x and y, a time series (see grDevices::xy.coords() for details), or a simple features object from package sf. y a vector of y coordinates. Only needs to be provided if x is vector. precision the precision to use when computing the center

Value

A list with items

x	x coordinate of the center
y	y coordinate of the center
dist	distance to the enclosing polygon

See Also

poi()

Examples

p1 <- rbind(
  c(0, 0),
  c(1, 0),
  c(3, 2),
  c(2, 4),
  c(1, 4),
  c(0, 0),
  c(NA, NA),
  c(1, 1),
  c(1, 2),
  c(2, 2),
  c(1, 1)
)
p2 <- rbind(
  c(3, 0),
  c(4, 0),
  c(4, 1),
  c(3, 1),
  c(3, 0),
  c(NA, NA),
  c(3.3, 0.8),
  c(3.8, 0.8),
  c(3.8, 0.3),
  c(3.3, 0.3),
  c(3.3, 0.3)
)
p3 <- rbind(
  c(3, 3),
  c(4, 2),
  c(4, 3),
  c(3, 3)
)
mpol <- list(p1, p2, p3)

plot.new()
plot.window(c(0, 4), c(0, 4), asp = 1)
for (i in seq_along(mpol)) {
  polypath(mpol[[i]])
}

res <- poi_multi(mpol, precision = 1e-5)
points(res, pch = 19, col = "steelblue4")

res

polylabelr documentation built on April 4, 2025, 1:50 a.m.