The concaveman function ports the 'concaveman' (<https://github.com/mapbox/concaveman>) library from 'mapbox'. It computes the concave polygon(s) for one or several set of points.

Analyzes data from a Conconi et al. (1996) <doi:10.1055/s-2007-972887>
    treadmill fitness test where speed is augmented by a constant amount every
    set number of seconds to estimate the anaerobic (lactate) threshold speed
    and heart rate. It reads a TCX file, allows optional removal observations
    from before and after the actual test, fits a change-point linear model
    where the change-point is the estimate of the lactate threshold, and plots
    the data points and fit model. Details of administering the fitness test are
    provided in the package vignette. Functions work by default for Garmin
    Connect TCX exports but may require additional data preparation for heart
    rate, time, and speed data from other sources.

A set of utilities for matching products in different
	     classification codes used in international trade
	     research. It supports concordance between the Harmonized
	     System (HS0, HS1, HS2, HS3, HS4, HS5, HS combined), the Standard 
	     International Trade Classification (SITC1, SITC2, SITC3, SITC4), 
	     the North American Industry Classification System (NAICS combined),
	     as well as the Broad Economic Categories (BEC), the International 
	     Standard of Industrial Classification (ISIC), and the Standard Industrial 
	     Classification (SIC). It also provides code nomenclature/descriptions 
	     look-up, Rauch classification look-up (via concordance to SITC2), and
	     trade elasticity look-up (via concordance to HS0 or SITC3
	     codes).

The Concordance Test is a non-parametric method for testing whether two o more samples originate from the same distribution. It extends the Kendall Tau correlation coefficient when there are only two groups. For details, see Alcaraz J., Anton-Sanchez L., Monge J.F. (2022) The Concordance Test, an Alternative to Kruskal-Wallis Based on the Kendall-tau Distance: An R Package. The R Journal 14, 26–53 <doi:10.32614/RJ-2022-039>.