Median Center

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.

Usage

median_center(x, group, weight, ...)

Arguments

x

Input POINT or POLYGON simple features

group

column name(s) specifying groups to calculate individual mean centers for

weight

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

...

expressions passed to dplyr::summarise()

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")
#> Simple feature collection with 2 features and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 542595.8 ymin: -147278.5 xmax: 582550.3 ymax: 482712.9
#> Projected CRS: USA_Contiguous_Albers_Equal_Area_Conic
#> # A tibble: 2 × 2
#>   grp               geometry
#> * <chr>          <POINT [m]>
#> 1 a      (542595.8 482712.9)
#> 2 b     (582550.3 -147278.5)

x_transformed |>
  dplyr::group_by(grp) |>
  median_center(weight = "wt")
#> Simple feature collection with 2 features and 1 field
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: 542595.8 ymin: -147278.5 xmax: 582550.3 ymax: 482712.9
#> Projected CRS: USA_Contiguous_Albers_Equal_Area_Conic
#> # A tibble: 2 × 2
#>   grp               geometry
#> * <chr>          <POINT [m]>
#> 1 a      (542595.8 482712.9)
#> 2 b     (582550.3 -147278.5)