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Forward geocoding

Source: R/oc_forward.R
oc_forward.Rd

Forward geocoding from a character vector of location names to latitude and longitude tuples.

Usage

oc_forward(
  placename,
  return = c("df_list", "json_list", "geojson_list", "url_only"),
  bounds = NULL,
  proximity = NULL,
  countrycode = NULL,
  language = NULL,
  limit = 10L,
  min_confidence = NULL,
  no_annotations = TRUE,
  roadinfo = FALSE,
  no_dedupe = FALSE,
  abbrv = FALSE,
  address_only = FALSE,
  add_request = FALSE,
  ...
)

Arguments

placename

A character vector with the location names or addresses to be geocoded.

If the locations are addresses, see OpenCage's instructions on how to format addresses for best forward geocoding results.

return

A character vector of length one indicating the return value of the function, either a list of tibbles (df_list, the default), a JSON list (json_list), a GeoJSON list (geojson_list), or the URL with which the API would be called (url_only).

bounds

A list of bounding boxes of length one or length(placename). Bounding boxes are named numeric vectors, each with four coordinates forming the south-west and north-east corners of the bounding box: list(c(xmin, ymin, xmax, ymax)). bounds restricts the possible results to the supplied region. It can be specified with the oc_bbox() helper. For example: bounds = oc_bbox(-0.563160, 51.280430, 0.278970, 51.683979). Default is NULL.

proximity

A list of points of length one or length(placename). A point is a named numeric vector of a latitude, longitude coordinate pair in decimal format. proximity provides OpenCage with a hint to bias results in favour of those closer to the specified location. It can be specified with the oc_points() helper. For example: proximity = oc_points(51.9526, 7.6324). Default is NULL.

countrycode

A two letter code as defined by the ISO 3166-1 Alpha 2 standard that restricts the results to the given country or countries. E.g. "AR" for Argentina, "FR" for France, "NZ" for the New Zealand. Multiple countrycodes per placename must be wrapped in a list. Default is NULL.

language

An IETF BCP 47 language tag (such as "es" for Spanish or "pt-BR" for Brazilian Portuguese). OpenCage will attempt to return results in that language. Alternatively you can specify the "native" tag, in which case OpenCage will attempt to return the response in the "official" language(s). In case the language parameter is set to NULL (which is the default), the tag is not recognized, or OpenCage does not have a record in that language, the results will be returned in English.

limit

Numeric vector of integer values to determine the maximum number of results returned for each placename. Integer values between 1 and 100 are allowed. Default is 10.

min_confidence

Numeric vector of integer values between 0 and 10 indicating the precision of the returned result as defined by its geographical extent, (i.e. by the extent of the result's bounding box). See the API documentation for details. Only results with at least the requested confidence will be returned. Default is NULL.

no_annotations

Logical vector indicating whether additional information about the result location should be returned. TRUE by default, which means that the results will not contain annotations.

roadinfo

Logical vector indicating whether the geocoder should attempt to match the nearest road (rather than an address) and provide additional road and driving information. Default is FALSE.

no_dedupe

Logical vector (default FALSE), when TRUE the results will not be deduplicated.

abbrv

Logical vector (default FALSE), when TRUE addresses in the formatted field of the results are abbreviated (e.g. "Main St." instead of "Main Street").

address_only

Logical vector (default FALSE), when TRUE only the address details are returned in the formatted field of the results, not the name of a point-of-interest should there be one at this address.

add_request

Logical vector (default FALSE) indicating whether the request is returned again with the results. If the return value is a df_list, the query text is added as a column to the results. json_list results will contain all request parameters, including the API key used! This is currently ignored by OpenCage if return value is geojson_list.

...

Ignored.

Value

Depending on the return argument, oc_forward returns a list with either

  • the results as tibbles ("df_list", the default),

  • the results as JSON specified as a list ("json_list"),

  • the results as GeoJSON specified as a list ("geojson_list"), or

  • the URL of the OpenCage API call for debugging purposes ("url_only").

When the results are returned as (a list of) tibbles, the column names coming from the OpenCage API are prefixed with "oc_".

See also

oc_forward_df() for inputs as a data frame, or oc_reverse() and oc_reverse_df() for reverse geocoding. For more information about the API and the various parameters, see the OpenCage API documentation.

Examples

if (FALSE) { # oc_key_present() && oc_api_ok()

# Geocode a single location, an address in this case
oc_forward(placename = "Triererstr 15, 99432, Weimar, Deutschland")

# Geocode multiple locations
locations <- c("Nantes", "Hamburg", "Los Angeles")
oc_forward(placename = locations)

# Use bounding box to help return accurate results
# for each placename
bounds <- oc_bbox(
  xmin = c(-2, 9, -119),
  ymin = c(47, 53, 34),
  xmax = c(0, 10, -117),
  ymax = c(48, 54, 35)
)
oc_forward(placename = locations, bounds = bounds)

# Another way to help specify the desired results
# is with country codes.
oc_forward(
  placename = locations,
  countrycode = c("ca", "us", "co")
)

# With multiple countrycodes per placename
oc_forward(
  placename = locations,
  countrycode = list(c("fr", "ca"), c("de", "us"), c("us", "co"))
)

# Return results in a preferred language if possible
oc_forward(
  placename = c("Brugge", "Mechelen", "Antwerp"),
  language = "fr"
)

# Limit the number of results per placename and return json_list
oc_forward(
  placename = locations,
  bounds = bounds,
  limit = 1,
  return = "json_list"
)
}