getPointsOutAlphaHull: Generate Spatial object from Alpha Hull object

In occTest: Characterizing and Filtering Species Occurrence Data

Generate Spatial object from Alpha Hull object

Description

Generate polygon based on alpha hulls at a given alpha parmater

Usage

getPointsOutAlphaHull(
  x,
  alpha = 2,
  coordHeaders = c("Longitude", "Latitude"),
  proj = "+proj=longlat +datum=WGS84",
  verbose = FALSE,
  alphaCap = 20
)

Arguments

x	dataframe of coordinates in decimal degrees, with a minimum of 3 rows.
alpha	the starting value for alpha.
coordHeaders	the column names for the longitude and latitude columns, respectively. If x has two columns, these are assumed to be longitude and latitude, and coordHeaders is ignored.
proj	the projection information for x. The default is currently the only supported option.
verbose	logical. print messages? Default to FALSE
alphaCap	Max alpha value before function aborts and returns a minimum convex hull.

Details

Based on rangeBuilder::getDynamicRange without cropping to sea and without increments alpha = initialAlpha, and will then increase alpha by alphaIncrement until both the fraction and partCount conditions are met.

If the conditions cannot be satisfied, then a minimum convex hull is returned.

If clipToCoast is set to "terrestrial" or "aquatic", the resulting polygon is clipped to the coastline, using the dataset provided with this package.

Value

a list with 2 elements:

hull	a SpatialPolygons object
alpha	the alpha value that was found to satisfy the criteria. If a convex hull was returned, this will list MCH.

Author(s)

Pascal Title (original version), Josep M Serra-Diaz (modifs)

See Also

Alpha hulls are created with ahull.

occTest documentation built on Nov. 18, 2022, 5:07 p.m.