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Check a region map against an independently derived assignment

Source: R/region_map.R
region_map_second_route.Rd

Compares the region each unit was assigned with the region a DIFFERENT method assigns it, and marks the disagreements that are already known and explained.

Usage

region_map_second_route(map, unit, region, route, known = character())

Arguments

map

Data frame, one row per unit.

unit

Name of the unit identifier column.

region

Name of the assigned region column.

route

Named character vector, or a data frame with the same two column names, giving the second method's assignment. Units it does not cover are skipped rather than counted as disagreements.

known

Units whose disagreement is expected and documented – the cases the second route is known to get wrong.

Value

A data frame of disagreements: unit, primary, second and known. sum(!x$known) is the number of unexplained disagreements and zero is the passing value; nrow(x) should equal the number of documented cases, because a documented case that stops disagreeing means the second route changed underneath the documentation.

Details

This is the only check here that can catch an error in the original method, because it does not use that method. Recomputing point in polygon against the same boundary file proves the pipeline is deterministic; deriving the region a second way – from a name, a postal geography, an administrative lookup – can disagree, and a disagreement is information either way round.

The known argument exists because a second route usually has understood weaknesses: a place name that is a community rather than a municipality, an amalgamated city, a township absorbed into a neighbour. Listing them keeps the check sharp instead of loosening the tolerance until everything passes, and listing them by NAME means an unexpected disagreement cannot hide inside an allowance.

See also

region_map_compare(), region_map_integrity()

Examples

cw <- data.frame(inst = c("North Jail", "South Jail", "Hill Jail"),
                 cd = c("3557", "3520", "3506"),
                 stringsAsFactors = FALSE)

# a name-based route that is known to mis-place one unit
route <- c("North Jail" = "3557", "South Jail" = "3520",
           "Hill Jail" = "3519")
region_map_second_route(cw, "inst", "cd", route, known = "Hill Jail")
#>        unit primary second known
#> 1 Hill Jail    3506   3519  TRUE

# an undocumented disagreement is what the check is for
route["South Jail"] <- "3521"
d <- region_map_second_route(cw, "inst", "cd", route, known = "Hill Jail")
sum(!d$known)
#> [1] 1