Build composite group keys from multiple columns

Creates a character vector of composite group identifiers by combining values from two or more columns of a data frame or sf object. The result is suitable as the region column of an offset data frame, and is the key building block for parent-to-child layout inheritance in hierarchical spatial datasets where child names repeat across parents.

Usage

make_hierarchy_key(x, cols)

Arguments

x

A data frame or sf object.

cols

A character vector of column names to combine into a composite key. At least one column is required. Columns must exist in x.

Value

A character vector of length nrow(x).

Details

When length(cols) == 1, the values of that column are returned directly (after whitespace trimming and NA replacement). When length(cols) > 1, values are joined as "col1=val1 | col2=val2 | ...".

See also

inherit_layout() to propagate parent offsets to child groups, create_layout_snapshot() to capture a layout for later restoration.

Examples

df <- data.frame(
  county = c("Essex", "Essex", "Morris"),
  mun    = c("Fairfield", "Caldwell", "Fairfield")
)
# Single column: values returned as-is
make_hierarchy_key(df, "county")
#> [1] "Essex"  "Essex"  "Morris"

# Two columns: composite key disambiguates repeated child names
make_hierarchy_key(df, c("county", "mun"))
#> [1] "county=Essex | mun=Fairfield"  "county=Essex | mun=Caldwell"  
#> [3] "county=Morris | mun=Fairfield"