Explode one selected section and keep the rest as context

explode_section() is a dashboard-oriented helper for exploratory maps. It applies an exploded layout only to the requested section, then recombines the untouched remainder of the layer as geographic context. The result can be passed directly to focus_map() with context_col to fade or hide the non-selected features.

Usage

explode_section(
  sf_obj,
  section_col,
  section,
  region_col = section_col,
  layout = c("explode", "grouped"),
  context = c("fade", "hide", "none"),
  role_col = ".explodemap_role",
  all_values = "all",
  ...
)

Arguments

sf_obj: Projected sf object.
section_col: Column containing the high-level sections users choose from, such as "North", "Central", and "South".
section: Selected section value. Values in all_values explode the full layer.
region_col: Column used for the explosion inside the selected section. Defaults to section_col. For municipality drill-downs, this is often a county column.
layout: "explode" for explode_sf() or "grouped" for explode_grouped().
context: "fade" or "hide" keeps non-selected features in the returned object as context; "none" drops them.
role_col: Name of the role column added to the output. Focus features are marked "focus" and context features are marked "context".
all_values: Values that mean "all sections". Default "all".
...: Passed to explode_sf() or explode_grouped().

Value

An exploded_map or grouped_exploded_map object with recombined focus/context geometry and extra diagnostics.

Examples

# \donttest{
poly <- function(xmin, ymin, xmax, ymax) {
  sf::st_polygon(list(rbind(
    c(xmin, ymin), c(xmax, ymin), c(xmax, ymax),
    c(xmin, ymax), c(xmin, ymin)
  )))
}

municipalities <- sf::st_sf(
  NAME = c("A", "B", "C", "D"),
  nj_region = c("South", "South", "North", "North"),
  county_name = c("Atlantic", "Cape May", "Bergen", "Hudson"),
  geometry = sf::st_sfc(
    poly(0, 0, 1000, 1000),
    poly(2000, 0, 3000, 1000),
    poly(0, 2000, 1000, 3000),
    poly(2000, 2000, 3000, 3000),
    crs = 3857
  )
)

focused <- explode_section(
  municipalities,
  section_col = "nj_region",
  section = "South",
  region_col = "county_name",
  alpha_r = 1800,
  alpha_l = 1200,
  plot = FALSE,
  quiet = TRUE
)

focus_map(
  focused,
  label_col = "NAME",
  context_col = ".explodemap_role",
  context_mode = "fade"
)

# }