photobiology (version 0.9.15)

day_night: Times for sun positions

Description

Functions for calculating the timing of solar positions by means of function sun_angles, given geographical coordinates and dates. They can be also used to find the time for an arbitrary solar elevation between 90 and -90 degrees by supplying "twilight" angle(s) as argument.

Usage

day_night(date = lubridate::today(), tz = Sys.timezone(),
  geocode = data.frame(lon = 0, lat = 51.5, address = "Greenwich"),
  twilight = "none", unit.out = "hours")
noon_time(date = lubridate::today(), tz = Sys.timezone(),
  geocode = data.frame(lon = 0, lat = 51.5, address = "Greenwich"),
  twilight = "none", unit.out = "datetime")
sunrise_time(date = lubridate::today(), tz = Sys.timezone(),
  geocode = data.frame(lon = 0, lat = 51.5, address = "Greenwich"),
  twilight = "sunlight", unit.out = "datetime")
sunset_time(date = lubridate::today(), tz = Sys.timezone(),
  geocode = data.frame(lon = 0, lat = 51.5, address = "Greenwich"),
  twilight = "sunlight", unit.out = "datetime")
day_length(date = lubridate::today(), tz = "UTC", geocode = data.frame(lon
  = 0, lat = 51.5, address = "Greenwich"), twilight = "sunlight",
  unit.out = "hours")
night_length(date = lubridate::today(), tz = "UTC",
  geocode = data.frame(lon = 0, lat = 51.5, address = "Greenwich"),
  twilight = "sunlight", unit.out = "hours")

Arguments

date

vector of POSIXct times or Date objects, any valid TZ is allowed, default is current date

tz

vector of character string indicating time zone to be used in output.

geocode

data frame with one or more rows and variables lon and lat as numeric values (degrees).

twilight

character string, one of "none", "civil", "nautical", "astronomical", or a numeric vector of length one, or two, giving solar elevation angle(s) in degrees (negative if below the horizon).

unit.out

charater string, One of "datetime", "hour", "minute", or "second".

Value

A data.fraame with variables day, tz, twilight.rise, twilight.set, longitude, latitude, address, sunrise, noon, sunset, daylength, nightlength.

noon_time, sunrise_time and sunset_time return a vector of POSIXct times

day_length and night_length return numeric a vector giving the length in hours

Details

Twilight names are interpreted as follows. "none": solar elevation = 0 degrees. "refraction": solar elevation = 0 degrees + refraction correction. "sunlight": upper rim of solar disk corrected for refraction. "civil": -6 degrees, "naval": -12 degrees, and "astronomical": -18 degrees. Unit names for output are as follows: "hours" times for sunrise and sunset are returned as times-of-day in hours since middnight. "date" or "datetime" return the same times as datetime objects with TZ set (this is much slower the "hours"). Day length and night length are always returned as numeric values expressed in hours.

See Also

Other astronomy related functions: format.solar_time, is.solar_time, print.solar_time, solar_time, sun_angles

Examples

library(lubridate)
my.geocode <- data.frame(lat = 60, lon = 25)
day_night(ymd("2015-05-30"), geocode = my.geocode, twilight = "civil")