Compare the archive versions of one force-month file

Reads every available version of a file and reports what differs: the number of rows, and for street and outcomes files the crime identifiers present in one version but not another. Street files routinely differ between snapshots only in their Last outcome category column, which is why row and identifier counts, not checksums, decide whether a force re-supplied a month.

Usage

lamp_version_diff(
  snapshot,
  force,
  month,
  file_type = c("street", "outcomes", "stop-and-search"),
  fetch = FALSE
)

Arguments

snapshot

A lamp_snapshot from lamp_archive_snapshot().

force

A police.uk force identifier.

month

A month as "YYYY-MM" or a Date.

file_type

One of "street", "outcomes", "stop-and-search".

fetch

Fetch versions that are listed but not held locally (needs network access).

Value

A tibble with one row per version: archive, n_rows, n_ids (distinct crime identifiers; NA for stop-and-search files), ids_not_in_others (identifiers absent from every other version) and crc32. The attribute outcome_changes gives, for street files, the number of shared crimes whose last outcome category differs between the oldest and newest versions.

See also

Other ingest: lamp_archive_download(), lamp_archive_index(), lamp_archive_register(), lamp_archive_snapshot(), lamp_list_versions(), lamp_lsoa_vintage(), lamp_read_crime(), lamp_read_outcomes(), lamp_read_stop_counts(), lamp_s60_legislation(), lamp_select_version()

Examples

cache <- tempfile("streetlamp-cache-")
zips <- list.files(
  system.file("extdata", "archive", package = "streetlamp"),
  pattern = "zip$", full.names = TRUE
)
for (z in zips) lamp_archive_register(z, dir = cache)
#> Registered archive "2026-06" from
#> /home/runner/work/_temp/Library/streetlamp/extdata/archive/2026-06.zip.
#> Registered archive "2026-07" from
#> /home/runner/work/_temp/Library/streetlamp/extdata/archive/2026-07.zip.
snap <- lamp_archive_snapshot(cache)
lamp_version_diff(snap, "west-yorkshire", "2026-05", "outcomes")
#> # A tibble: 2 × 5
#>   archive n_rows n_ids ids_not_in_others crc32   
#>   <chr>    <int> <int>             <int> <chr>   
#> 1 2026-06   1761  1728                 3 efe93414
#> 2 2026-07   1756  1725                 0 34133345