# poi

0th

Percentile

##### Pole of Inaccessibility (Visual Center) of a Polygon

This function computes and returns the approximate pole of inaccessibility for a polygon using a quadtree-based algorithm developed by the people from Mapbox.

##### Usage
poi(x, y = NULL, precision = 1)
##### Arguments
x

a vector of x coordinates or a matrix or data.frame of x and y coordinates, a list of components x and y, or a time series (see grDevices::xy.coords() for details)

y

a vector of y coordinates. Only needs to be provided if x is vector.

precision

the precision to use when computing the center

##### Details

If there are any NA values in the input, they will be treated as separators for multiple paths (rings) of the polygon, mimicking the behavior of graphics::polypath().

##### Value

A list with items

x

x coordinate of the center

y

y coordinate of the center

dist

distance to the enclosing polygon

grDevices::xy.coords(), graphics::polypath()

• poi
##### Examples
# NOT RUN {
plot_path <- function(x, y, ...) {
plot.new()
plot.window(range(x, na.rm = TRUE), range(y, na.rm = TRUE))
polypath(x, y, ...)
}

x <- c(5, 10, 10, 5, 5, 6, 6, 7, 7, 6, 8, 8, 9, 9, 8)
y <- c(5, 5, 10, 10, 5, 6, 7, 7, 6, 6, 8, 9, 9, 8, 8)

plot_path(x, y, col = "grey", border = NA)

points(poi(x, y))

# }

Documentation reproduced from package polylabelr, version 0.1.0, License: MIT + file LICENSE

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