Customise your query

countrycode

The countrycode parameter restricts the results to the given country. The country code is a two letter code as defined by the ISO 3166-1 Alpha 2 standard. E.g. “AR” for Argentina, “FR” for France, and “NZ” for the New Zealand.

oc_forward_df(placename = "Paris", countrycode = "US", limit = 5)

Multiple countrycodes per placename must be wrapped in a list. Here is an example with places called “Paris” in Italy and Portugal.

oc_forward_df(placename = "Paris", countrycode = list(c("IT", "PT")), limit = 5)

Despite the name, country codes also exist for territories that are not independent states, e.g. Gibraltar (“GI”), Greenland (“GL”), Guadaloupe (“GP”), or Guam (“GU”). You can look up specific country codes with the {ISOcodes} or {countrycodes} packages or on the ISO or Wikipedia webpages. In fact, you can also look up country codes via OpenCage as well. If you were interested in the country code of Curaçao for example, you could run:

oc_forward_df("Curaçao", no_annotations = FALSE)["oc_iso_3166_1_alpha_2"]

bounds

The bounds parameter restricts the possible results to a defined bounding box. A bounding box is a named numeric vector with four coordinates specifying its south-west and north-east corners: (xmin, ymin, xmax, ymax). The bounds parameter can most easily be specified with the oc_bbox() helper. For example, bounds = oc_bbox(-0.56, 51.28, 0.27, 51.68). OpenCage provides a ‘bounds-finder’ to interactively determine bounds values.

Below is an example of the use of bounds where the bounding box specifies the the South American continent.

oc_forward_df(placename = "Paris", bounds = oc_bbox(-97, -56, -32, 12), limit = 5)

Again, you can also use {opencage} to determine a bounding box for subsequent queries. If you wanted to see how many Plaça d’Espanya there are on the Balearic Islands, for example, you could find the appropriate bounding box and then search for the squares:

hi <- oc_forward_df(placename = "Balearic Islands", no_annotations = FALSE)

hi_bbox <-
  oc_bbox(
    hi$oc_southwest_lng,
    hi$oc_southwest_lat,
    hi$oc_northeast_lng,
    hi$oc_northeast_lat
  )

oc_forward_df(placename = "Plaça d'Espanya", bounds = hi_bbox, limit = 20)

Note that OpenCage does not support point-of-interest or feature search, like “show me all bus stops in this area”. If you are more interested in these kind of features, you might want to take a look at the {osmdata} package.

proximity

The proximity parameter provides OpenCage with a hint to bias results in favour of those closer to the specified location. It is just one of many factors used for ranking results, however, and (some) results may be far away from the location or point passed to the proximity parameter. A point is a named numeric vector of a latitude and longitude coordinate pair in decimal format. The proximity parameter can most easily be specified with the oc_points() helper. For example, proximity = oc_point(38.0, -84.5), if you happen to already know the coordinates. If not, you can also look them up with {opencage}, of course:

lx <- oc_forward_df("Lexington, Kentucky")

lx_point <- oc_points(lx$oc_lat, lx$oc_lng)

oc_forward_df(placename = "Paris", proximity = lx_point, limit = 5)

Note that the French capital is listed before other places in the US, which are closer to the point provided. This illustrates how proximity is only one of many factors influencing the ranking of results.

Confidence

min_confidence — an integer value between 0 and 10 — indicates the precision of the returned result as defined by its geographical extent, i.e. by the extent of the result’s bounding box. When you specify min_confidence, only results with at least the requested confidence will be returned. Thus, in the following example, the French capital is too large to be returned.

oc_forward_df(placename = "Paris", min_confidence = 7, limit = 5)

Note that confidence is not used for the ranking of results. It does not tell you which result is more “correct” or “relevant”, nor what type of thing the result is, but rather how small a result is, geographically speaking. See the API documentation for details.

language

If you would like to get your results in a specific language, you can pass an IETF BCP 47 language tag, such as “tr” for Turkish or “pt-BR” for Brazilian Portuguese, to the language parameter. OpenCage will attempt to return results in that language.

oc_forward_df(placename = "Munich", language = "tr")

Alternatively, you can specify the “native” tag, in which case OpenCage will attempt to return the response in the “official” language(s) of the location. Keep in mind, however, that some countries have more than one official language or that the official language may not be the one actually used day-to-day.

oc_forward_df(placename = "Munich", language = "native")

If 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.

oc_forward_df(placename = "München")

To find the correct language tag for your desired language, you can search for the language on the BCP47 language subtag lookup for example. Note however, that there are some language tags in use on OpenStreetMap, one of OpenCage’s main sources, that do not conform with the IETF BCP 47 standard. It might, therefore, be helpful to consult the details page of the target country on openstreetmap.org to see which language tags are actually used. In any case, neither the OpenCage API nor the functions in this package will validate the language tags you provide.

For further details, see OpenCage’s API documentation.

Annotations

OpenCage supplies additional information about the result location in what it calls annotations. Annotations include, among a variety of other types of information, country information, time of sunset and sunrise, UN M49 codes or the location in different geocoding formats, like Maidenhead, Mercator projection (EPSG:3857), geohash or what3words. Some annotations, like the Irish Transverse Mercator (ITM, EPSG:2157) or the Federal Information Processing Standards (FIPS) code will only be shown when appropriate.

Whether the annotations are shown, is controlled by the no_annotations argument. It is TRUE by default, which means that the output will not contain annotations. When you set no_annotations to FALSE, all columns are returned (i.e. output is implicitly set to "all"). This leads to a result with a lot of columns.

oc_forward_df("Dublin", no_annotations = FALSE) |> colnames()
#>  [1] "placename"                         "oc_lat"                            "oc_lng"                            "oc_confidence"                     "oc_formatted"                      "oc_mgrs"                           "oc_maidenhead"                     "oc_callingcode"                    "oc_flag"                          
#> [10] "oc_geohash"                        "oc_qibla"                          "oc_wikidata"                       "oc_dms_lat"                        "oc_dms_lng"                        "oc_itm_easting"                    "oc_itm_northing"                   "oc_mercator_x"                     "oc_mercator_y"                    
#> [19] "oc_nuts_nuts0_code"                "oc_nuts_nuts1_code"                "oc_nuts_nuts2_code"                "oc_nuts_nuts3_code"                "oc_osm_edit_url"                   "oc_osm_note_url"                   "oc_osm_url"                        "oc_un_m49_statistical_groupings"   "oc_un_m49_regions_europe"         
#> [28] "oc_un_m49_regions_ie"              "oc_un_m49_regions_northern_europe" "oc_un_m49_regions_world"           "oc_currency_alternate_symbols"     "oc_currency_decimal_mark"          "oc_currency_html_entity"           "oc_currency_iso_code"              "oc_currency_iso_numeric"           "oc_currency_name"                 
#> [37] "oc_currency_smallest_denomination" "oc_currency_subunit"               "oc_currency_subunit_to_unit"       "oc_currency_symbol"                "oc_currency_symbol_first"          "oc_currency_thousands_separator"   "oc_roadinfo_drive_on"              "oc_roadinfo_speed_in"              "oc_sun_rise_apparent"             
#> [46] "oc_sun_rise_astronomical"          "oc_sun_rise_civil"                 "oc_sun_rise_nautical"              "oc_sun_set_apparent"               "oc_sun_set_astronomical"           "oc_sun_set_civil"                  "oc_sun_set_nautical"               "oc_timezone_name"                  "oc_timezone_now_in_dst"           
#> [55] "oc_timezone_offset_sec"            "oc_timezone_offset_string"         "oc_timezone_short_name"            "oc_what3words_words"               "oc_northeast_lat"                  "oc_northeast_lng"                  "oc_southwest_lat"                  "oc_southwest_lng"                  "oc_iso_3166_1_alpha_2"            
#> [64] "oc_iso_3166_1_alpha_3"             "oc_iso_3166_2"                     "oc_category"                       "oc_normalized_city"                "oc_type"                           "oc_city"                           "oc_continent"                      "oc_country"                        "oc_country_code"                  
#> [73] "oc_county"                         "oc_county_code"                    "oc_political_union"                "oc_region"

roadinfo

roadinfo indicates whether the geocoder should attempt to match the nearest road (rather than an address) and provide additional road and driving information. It is FALSE by default, which means OpenCage will not attempt to match the nearest road. Some road and driving information is nevertheless provided as part of the annotations (see above), even when roadinfo is set to FALSE.

library(dplyr, warn.conflicts = FALSE)
oc_forward_df(placename = c("Europa Advance Rd", "Bovoni Rd"), roadinfo = TRUE) |>
select(placename, contains("roadinfo"))

A blog post provides more details.

Abbreviated addresses

The geocoding functions also have an abbr parameter, which is FALSE by default. When it is TRUE, the addresses in the formatted field of the results are abbreviated (e.g. “Main St.” instead of “Main Street”).

oc_forward_df("Wall Street")

oc_forward_df("Wall Street", abbrv = TRUE)

See this blog post for more information.

address_only

When address_only is set to TRUE (by default FALSE), OpenCage will attempt to exclude names of points-of-interests from the formatted field of the results. In the following example, the POI “Hôtel de ville de Nantes” (town hall of Nantes) is removed from the oc_formatted column with address_only = TRUE.

oc_reverse_df(47.21947, -1.54754)

oc_reverse_df(47.21947, -1.54754, address_only = TRUE)