Package 'centr'

Title: Weighted and Unweighted Spatial Centers
Description: Generate mean and median weighted or unweighted spatial centers. Functions are analogous to their identically named counterparts within 'ArcGIS Pro'. Median center methodology based off of Kuhn and Kuenne (1962) <doi:10.1111/j.1467-9787.1962.tb00902.x>.
Authors: Ryan Zomorrodi [aut, cre, cph]
Maintainer: Ryan Zomorrodi <[email protected]>
License: MIT + file LICENSE
Version: 0.2.0
Built: 2024-11-30 04:18:47 UTC
Source: https://github.com/ryanzomorrodi/centr

Help Index


Mean Center

Description

Mean center calculates the geographic average center. One can specify the groups to calculate individual centers for groups and weights for each individual point. It is analagous to the ArcGIS Pro Mean Center tool.

If st_is_longlat(x), mean center is calculated assuming a spherical Earth. Projected data is calculated assuming a "flat" Earth.

Usage

mean_center(x, group = NULL, weight = NULL)

Arguments

x

Input POINT or POLYGON simple features

group

name of character column specifying groups to calculate individual mean centers for

weight

name of numeric weight column specifying an individual point's contribution to the mean center

Value

An sf object with a mean center for each group

Examples

df <- data.frame(
  lon = c(20, 50, 30, 80, 10),
  lat = c(25, 70, 30, 50, 30),
  grp = c("a", "b", "a", "b", "a"),
  wt = c(1, 5, 1, 3, 2)
)
x <- sf::st_as_sf(df, coords = c("lon", "lat"), crs = 4326)
mean_center(x, group = "grp", weight = "wt")

Median Center

Description

Median center iteratively calculates the point that minimizes distance to all features. One can specify the groups to calculate individual centers for and weights for each individual point. It is analagous to the ArcGIS Pro Median Center tool.

It uses the methodology introduced by Kuhn and Kuenne (1962).

Currently, median center is only implemenented for projected data.

Usage

median_center(x, group = NULL, weight = NULL, tolerance = 1e-04)

Arguments

x

Input POINT, MULTIPOINT, POLYGON, or MULTIPOLYGON simple features

group

name of character column specifying groups to calculate individual median centers for

weight

name of numeric weight column specifying an individual point's contribution to the median center

tolerance

numeric threshold determining when an estimate improvement is sufficiently small enough to stop iterating (smaller = slower, but more precision)

Value

An sf object with a median center for each group

Examples

df <- data.frame(
  lon = c(-88, -90, -92, -89, -90),
  lat = c(42, 40, 30, 32, 42),
  grp = c("a", "b", "a", "b", "a"),
  wt = c(1, 1, 1, 1, 1)
)
x <- sf::st_as_sf(df, coords = c("lon", "lat"), crs = 4326)
x_transformed <- sf::st_transform(x, crs = "ESRI:102003")
median_center(x_transformed, group = "grp", weight = "wt")