This function downloads the NAR data if necessary and returns a connection to the NAR database.
The StatCan release is one ~1.7 GB zip whose member files are split by province, and the server honours HTTP range requests, so `provinces` can restrict the download to the provinces that are actually wanted – 192 MB for British Columbia, 10 MB for Prince Edward Island. The addresses are the same NAR rows either way, so a partial database geocodes its own provinces exactly as well as a national one does; it simply holds nothing outside them, which [geocode()] reports as `not_covered` rather than as a failure to match.
Coverage is recorded in the database and checked before anything is downloaded. A national database already satisfies every request, and asking for a province an existing partial database lacks adds just that province rather than rebuilding.
Arguments
- version
Version of the NAR database to connect to. Default is "latest".
- provinces
Provinces to make available, as two-letter abbreviations, SGC codes or full names – or `"all"` for the whole country. `NULL`, the default, keeps whatever a cached database already holds; when there is nothing cached it prompts in an interactive session and downloads the whole country otherwise.
- refresh
Logical indicating whether to refresh the local cache of the NAR database.
Examples
if (FALSE) { # \dontrun{
con <- nar_connection()
# British Columbia only: 192 MB rather than 1.7 GB.
bc <- nar_connection(provinces = "BC")
nar_provinces(bc)
# Add a province to an existing partial database.
bc_ab <- nar_connection(provinces = c("BC", "AB"))
} # }