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Add a feature to an Overpass query

Usage

add_osm_feature(
  opq,
  key,
  value,
  key_exact = TRUE,
  value_exact = TRUE,
  match_case = TRUE,
  bbox = NULL
)

Arguments

opq

An overpass_query object

key

feature key

value

value for feature key; can be negated with an initial exclamation mark, value = "!this", and can also be a vector, value = c ("this", "that").

key_exact

If FALSE, key is not interpreted exactly; see https://wiki.openstreetmap.org/wiki/Overpass_API

value_exact

If FALSE, value is not interpreted exactly

match_case

If FALSE, matching for both key and value is not sensitive to case

bbox

optional bounding box for the feature query; must be set if no opq query bbox has been set

Value

opq object

Note

key_exact should generally be TRUE, because OSM uses a reasonably well defined set of possible keys, as returned by available_features. Setting key_exact = FALSE allows matching of regular expressions on OSM keys, as described in Section 6.1.5 of https://wiki.openstreetmap.org/wiki/Overpass_API/Overpass_QL. The actual query submitted to the overpass API can be obtained from opq_string.

add_osm_feature vs add_osm_features

Features defined within an add_osm_features call are combined with a logical OR.

Chained calls to either add_osm_feature or add_osm_features() combines features from these calls in a logical AND; this is analagous to chaining dplyr::filter() on a data frame.

add_osm_features() with only one feature is logically equivalent to add_osm_feature().

Examples

if (FALSE) {
q <- opq ("portsmouth usa") %>%
    add_osm_feature (
        key = "amenity",
        value = "restaurant"
    ) %>%
    add_osm_feature (key = "amenity", value = "pub")
osmdata_sf (q) # all objects that are restaurants AND pubs (there are none!)
q1 <- opq ("portsmouth usa") %>%
    add_osm_feature (
        key = "amenity",
        value = "restaurant"
    )
q2 <- opq ("portsmouth usa") %>%
    add_osm_feature (key = "amenity", value = "pub")
c (osmdata_sf (q1), osmdata_sf (q2)) # all restaurants OR pubs
# Use of negation to extract all non-primary highways
q <- opq ("portsmouth uk") %>%
    add_osm_feature (key = "highway", value = "!primary")
}