Package 'lutz'

Create a list of Time Zones

Description

Output a list of time zone names, with daylight savings time and utc offset

Usage

tz_list()

Value

A data.frame of all time zones on your system. Columns:

• tz_name: the name of the time zone

• zone: time zone

• is_dst: is the time zone in daylight savings time

• utc_offset_h: offset from UTC (in hours)

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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"])
}

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Lookup time zones of lat/long pairs

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_coords(lat, lon, method = "fast", warn = TRUE)

Arguments

lat	numeric vector of latitudes
lon	numeric vector of longitudes the same length as x
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.

Value

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

Examples

tz_lookup_coords(42, -123)
tz_lookup_coords(lat = c(48.9, 38.5, 63.1, -25), lon = c(-123.5, -110.2, -95.0, 130))

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Find the offset from UTC at a particular date/time in a particular time zone

Description

Find the offset from UTC at a particular date/time in a particular time zone

Usage

tz_offset(dt, tz = "")

Arguments

dt	Date, POSIXt or date-like character string
tz	A time zone name from base::OlsonNames(). Not required if dt is a POSIXt object with a time zone component.

Value

a one-row data frame with details of the time zone

Examples

tz_offset("2018-06-12", "America/Moncton")

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Plot a time zone

Description

Make a circular plot of a time zone, visualizing the UTC offset over the course of the year, including Daylight Savings times

Usage

tz_plot(tz)

Arguments

tz	a valid time zone name. See OlsonNames()

Value

a ggplot2 object

Examples

tz_plot("America/Vancouver")

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