lutz: tz_lookup – R documentation

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tz_lookup

Lookup time zones of sf or sp points

Description

There are two methods - "fast", and "accurate". The "fast" version can look up many thousands of points very quickly, however when a point is near a time zone boundary and not near a populated centre, it may return the incorrect time zone. If accuracy is more important than speed, use method = "accurate".

Usage

tz_lookup(x, crs = NULL, method = "fast", warn = TRUE)

Arguments

`x`	either an `sfc` or `sf` points or `SpatialPoints(DataFrame)` object
`crs`	the coordinate reference system: integer with the EPSG code, or character with proj4string. If not specified (i.e., `NULL`) and `x` has no existing `crs`, EPSG: 4326 is assumed (lat/long).
`method`	method by which to do the lookup. Either `"fast"` (default) or `"accurate"`.
`warn`	By default, if `method = "fast"` a warning is issued about the potential for inaccurate results. Set `warn` to `FALSE` to turn this off.

Details

Note that there are some regions in the world where a single point can land in two different overlapping time zones. The "accurate" method includes these, and when they are encountered they are concatenated in a single string, separated by a semicolon. The data used in the "fast" method does not include overlapping time zones at this time.

Value

character vector the same length as x specifying the time zone of the points.

Examples

if (require("sf")) {

state_pts <- lapply(seq_along(state.center$x), function(i) {
  st_point(c(state.center$x[i], state.center$y[i]))
})

state_centers_sf <- st_sf(st_sfc(state_pts))

state_centers_sf$tz <- tz_lookup(state_centers_sf)

plot(state_centers_sf[, "tz"])
}

lutz

Look Up Time Zones of Point Coordinates

v0.3.1

MIT + file LICENSE

Authors

Andy Teucher [aut, cre] (<https://orcid.org/0000-0002-7840-692X>), Bob Rudis [ctb] (<https://orcid.org/0000-0001-5670-2640>)

Initial release