Keeps only the atoms belonging to region at geoframe, and rebuilds the
member vocabularies accordingly. Geometry, when attached, is subset in step.
Arguments
- x
A
Geoscale.- geoframe
Geoframe that
regionbelongs to.- region
Character vector of region codes to keep.
- drop_empty_geoframes
Drop geoframes left with no codes at all.
Value
A Geoscale.
Details
A genuine subset is a SAMPLE and is book-kept as one (the spatial
mirror of timescales::filter_calendar()'s year_fraction):
meta$coverage records, per weight column, the kept fraction of the
ROOT parent's total (so filters compose against the original
object), meta$parent_totals stores those root totals (making the
coverage claim verifiable by the validator), meta$parent_name
records the parent, and meta$name is mangled to
"parent[geoframe:n]" so a sample never impersonates its parent in
the crosswalk registry or in join_geoscale() column names. A
filter that keeps every atom is a true no-op. Read the fraction back
with geoscale_coverage().
Examples
gs <- geoscale_example()
n <- filter_geoscale(gs, "country", "N")
n
#> Geoscale: example[country:N]
#> Description: Synthetic example: reused code, non-nesting geoframe pair, and an unassigned atom
#> Geoframes (4, coarsest first):
#> - country (1)
#> - state (2)
#> - zone (2)
#> - atom (4)
#> Atoms: 4
#> Weights: km2, pop (default: km2)
geoscale_coverage(n)
#> km2 pop
#> 0.3225806 0.6666667