Find the Pole of Inaccessibility (Visual Center) of a Polygon

A wrapper around the C++ library 'polylabel' from 'Mapbox', providing an efficient routine for finding the approximate pole of inaccessibility of a polygon, which usually serves as an excellent candidate for labeling of a polygon.

Travis buildstatus AppVeyor buildstatus Coveragestatus

polylabelr is an R wrapper for the polylabel package from Mapbox. It currently contains a single function, poi() that finds the pole of inaccessibility of a polygon, which usually makes for a good place to put a label on a polygon—hence the name.


# a concave polygon
x <- c(0, 4, 1, 6, 7, 7, 0, 0)
y <- c(0, 0, 1, 2, 1, 3, 2, 0)
# locate the pole of inaccessibility
p <- polylabelr::poi(x, y, precision = 0.01)
plot.window(range(x, na.rm = TRUE), range(y, na.rm = TRUE))
polypath(x, y, col = "grey", border = FALSE)


Development version



The source code from polylabel and geometry.hpp has been modified in a few ways to compile properly with c++11 using the standard flags required by CRAN policies. polylabel has also been modified to return the distance from the chosen point to the enclosing polygon, in case it is of value to users.


polylabelr 0.1.0

  • First release.

Reference manual

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0.2.0 by Johan Larsson, 2 years ago,

Report a bug at

Browse source code at

Authors: Johan Larsson [aut, cre] , Kent Johnson [ctb] , Mapbox [cph] (polylabel , variant , and geometry libraries)

Documentation:   PDF Manual  

MIT + file LICENSE license

Imports Rcpp

Suggests covr, testthat, spelling, sf

Linking to Rcpp

Imported by eulerr.

See at CRAN