check_contiguity: Check Contiguity by Group

In geomander: Geographic Tools for Studying Gerrymandering

Check Contiguity by Group

Description

Given a zero-indexed adjacency list and an array of group identifiers, this returns a tibble which identifies the connected components. The three columns are group for the inputted group, group_number which uniquely identifies each group as a positive integer, and component which identifies the connected component number for each corresponding entry of adjacency and group. If everything is connected within the group, then each element of component will be 1. Otherwise, the largest component is given the value 1, the next largest 2, and so on.

Usage

check_contiguity(adj, group)

cct(adj, group)

ccm(adj, group)

Arguments

adj	adjacency list
group	array of group identifiers. Typically district numbers or county names. Defaults to 1 if no input is provided, checking that the adjacency list itself is one connected component.

Details

If nothing is provided to group, it will default to a vector of ones, checking if the adjacency graph is connected.

cct() is shorthand for creating a table of the component values. If everything is connected within each group, it returns a value of 1. In general, it returns a frequency table of components.

ccm() is shorthand for getting the maximum component value. It returns the maximum number of components that a group is broken into. This returns 1 if each group is connected. #'

Value

tibble with a column for each of inputted group, created group number, and the identified connected component number

Examples

data(checkerboard)
adj <- adjacency(checkerboard)
# These each indicate the graph is connected.
check_contiguity(adj)
cct(adj)
ccm(adj)

geomander documentation built on April 16, 2023, 5:18 p.m.