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Inherit region offsets from a coarser to a finer grouping column

Source: R/hierarchy.R
inherit_layout.Rd

When switching from a parent grouping (e.g., county) to a child grouping (e.g., municipality), inherit_layout() maps the parent's drag offsets to every child region that belongs to each parent. Each child inherits the mean offset of the parent group it belongs to.

Usage

inherit_layout(x, from, to, parent_offsets)

Arguments

x

An sf object or data frame containing both from and to columns.

from

A character vector of one or more column names defining the coarser (parent) grouping. The region values in parent_offsets must match the keys produced by make_hierarchy_key(x, from).

to

A character vector of one or more column names defining the finer (child) grouping. The region column of the returned data frame will contain the keys produced by make_hierarchy_key(x, to).

parent_offsets

A data frame with region, dx_m, and dy_m columns keyed to the from grouping, as returned by read_offsets() or the Spatial Studio CSV export. Rows whose region does not match any parent key in x are silently ignored.

Value

A data frame with region, dx_m, and dy_m columns. Rows whose parent has no offset entry receive zero movement.

Details

When child names repeat across parents (e.g., "Fairfield" exists in both Essex and Morris counties), pass both columns in to so that composite keys are used: to = c("county", "mun"). The resulting region values will be composite strings like "county=Essex | mun=Fairfield", which can be passed directly to drag_map_prototype() or render_dragged_map() via make_hierarchy_key().

See also

make_hierarchy_key() for composite key construction, create_layout_snapshot() for capturing and restoring layouts.

Examples

poly <- sf::st_sf(
  county = c("Essex", "Essex", "Morris", "Morris"),
  mun    = c("Fairfield", "Caldwell", "Fairfield", "Roxbury"),
  geometry = sf::st_sfc(
    sf::st_polygon(list(rbind(c(0,1e5),c(1e5,1e5),c(1e5,2e5),c(0,2e5),c(0,1e5)))),
    sf::st_polygon(list(rbind(c(0,0),c(1e5,0),c(1e5,1e5),c(0,1e5),c(0,0)))),
    sf::st_polygon(list(rbind(c(1e5,1e5),c(2e5,1e5),c(2e5,2e5),c(1e5,2e5),c(1e5,1e5)))),
    sf::st_polygon(list(rbind(c(1e5,0),c(2e5,0),c(2e5,1e5),c(1e5,1e5),c(1e5,0)))),
    crs = 3857
  )
)
county_offsets <- data.frame(
  region = c("Essex", "Morris"),
  dx_m   = c(50000, -50000),
  dy_m   = c(0, 0)
)
# "Fairfield" repeats, so use composite to= key
mun_offsets <- inherit_layout(
  poly,
  from           = "county",
  to             = c("county", "mun"),
  parent_offsets = county_offsets
)
mun_offsets
#>                          region   dx_m dy_m
#> 1   county=Essex | mun=Caldwell  50000    0
#> 2  county=Essex | mun=Fairfield  50000    0
#> 3 county=Morris | mun=Fairfield -50000    0
#> 4   county=Morris | mun=Roxbury -50000    0