Find sibling codes within a hierarchical coding system

Given a code from a hierarchical coding system (e.g. NOC or SOC), returns all other codes that share the same immediate parent. If the target code has no siblings at its own level (i.e. it is an "only child"), the function falls back to returning first cousins – codes at the same level that share the same grandparent instead.

Usage

siblings(target_code, system)

Arguments

target_code

A character string giving the code to find siblings for. Must be a valid code within system.

system

A codingsystem object (as validated by is.codingsystem) containing a table element with, at minimum, code and parent columns.

Value

A character vector of sibling (or, failing that, first-cousin) codes. Returns character(0) if target_code has no parent, or if it has no parent and no grandparent from which cousins could be derived.

Details

The search proceeds in two steps:

1. Siblings: codes sharing target_code's immediate parent (excluding target_code itself).

2. Cousins: if no siblings are found, codes sharing a parent with target_code's parent (i.e. sharing a grandparent), excluding the parent itself. Because these are children of the parent's own siblings, they are automatically at the same hierarchical level as target_code.

The function does not climb beyond the grandparent level; if no siblings or cousins are found there, it returns character(0).

Examples

if (FALSE) { # \dontrun{
siblings("0013", noc2011_all)  # same-parent siblings
siblings("0311", noc2011_all)  # falls back to cousins, since 0311
                                # is an only child under its parent
} # }