Finds a location code for carbon_intensity without any
network access, in this order: the RMBL_LOCATION environment
variable (any code or name the table knows); codecarbon's
CODECARBON_COUNTRY_ISO_CODE (alpha-3), so a machine already
configured for codecarbon needs nothing more; the system time zone, mapped
to its country through the IANA zone tables (America/Toronto is
Canada, Europe/Berlin Germany); the territory in the locale
(en_CA.UTF-8 is Canada). When none of these yields a location in
the table the answer is "WORLD", and the method says so, so a report
never silently applies one country's grid to another's computation.
Usage
detect_location(
env_location = Sys.getenv("RMBL_LOCATION"),
codecarbon_location = Sys.getenv("CODECARBON_COUNTRY_ISO_CODE"),
tz = Sys.timezone(),
locale = Sys.getlocale("LC_TIME")
)Value
A list with location (a code present in
carbon_intensity_table()) and method (how it was found).
Details
The zone table (inst/extdata/timezone_countries.csv, built by
tools/build_timezones.R from the IANA database) holds every zone
of zone.tab, which names exactly one country per zone
(Europe/Stockholm is Sweden even though the database now keeps
its rules under Europe/Berlin), plus the aliases and old names of
the backward file under their own country: the country of the zone
the alias stood for before the database merged it (Iceland is
Atlantic/Reykjavik, Iceland, not Abidjan's Ivory Coast), the
link target's country when that target serves a single country
(Asia/Calcutta, US/Eastern), and a reviewed list for the
rest (Atlantic/Jan_Mayen, America/Coral_Harbour,
Canada/Eastern). Every geographic zone OlsonNames() lists
resolves to a country or territory; a territory the carbon table has no
row of its own for (Monaco, Jersey, Vaduz, the Antarctic stations) uses
the grid of the country it draws on or the world average, and the method
says which. The Etc/, UTC, fixed-offset and generic zones
(CET, EST, WET) name no country and fall through
to the locale.
Examples
detect_location()
#> $location
#> [1] "WORLD"
#>
#> $method
#> [1] "fallback, no location found in environment, time zone or locale"
#>
detect_location(env_location = "", codecarbon_location = "", tz = "Europe/Paris")
#> $location
#> [1] "FR"
#>
#> $method
#> [1] "system time zone Europe/Paris"
#>
detect_location(env_location = "", codecarbon_location = "", tz = "",
locale = "en_IN.UTF-8")
#> $location
#> [1] "IN"
#>
#> $method
#> [1] "locale en_IN.UTF-8"
#>
# an explicit setting wins over everything else
detect_location(env_location = "CA-QC", tz = "Europe/Paris")
#> $location
#> [1] "CA-QC"
#>
#> $method
#> [1] "RMBL_LOCATION environment variable"
#>
# nothing usable: the world average, and the method says so
detect_location(env_location = "", codecarbon_location = "", tz = "UTC", locale = "C")
#> $location
#> [1] "WORLD"
#>
#> $method
#> [1] "fallback, no location found in environment, time zone or locale"
#>