~hrbrmstr/daybreak

af8ff3a5efbe1173d1a188e6d8d884c2bc809e9c — hrbrmstr 4 months ago 3d72d27
plain C version
M .Rbuildignore => .Rbuildignore +1 -0
@@ 19,3 19,4 @@
^CRAN-RELEASE$
^appveyor\.yml$
^tools$
^LICENSE\.md$

M DESCRIPTION => DESCRIPTION +11 -10
@@ 1,24 1,25 @@
Package: daybreak
Type: Package
Title: daybreak title goes here otherwise CRAN checks fail
Title: Compute Sun Rise/Set Times, Start/End of Twilight, and the 
    Length of the Day at Any Date and Latitude
Version: 0.1.0
Date: 2019-12-31
Authors@R: c(
    person("Bob", "Rudis", email = "bob@rud.is", role = c("aut", "cre"), 
           comment = c(ORCID = "0000-0001-5670-2640"))
           comment = c(ORCID = "0000-0001-5670-2640")),
    person("Paul", "Schlyter", role = "aut", comment = "sunriset lib")
  )
Maintainer: Bob Rudis <bob@rud.is>
Description: A good description goes here otherwise CRAN checks fail.
Description: A wrapper for Paul Schlyter's C-based library for computing 
    sunrise, sunset, twilight start and end, plus the length of day for 
    a given data and coordinates.
URL: https://gitlab.com/hrbrmstr/daybreak
BugReports: https://gitlab.com/hrbrmstr/daybreak/issues
Encoding: UTF-8
License: AGPL
Suggests:
    covr
Depends:
NeedsCompilation: yes
License: MIT + file LICENSE
Depends: 
    R (>= 3.2.0)
Imports:
    httr,
    jsonlite
Roxygen: list(markdown = TRUE)
RoxygenNote: 7.0.2
Suggests: tinytest

A LICENSE => LICENSE +2 -0
@@ 0,0 1,2 @@
YEAR: 2019
COPYRIGHT HOLDER: Bob Rudis

A LICENSE.md => LICENSE.md +21 -0
@@ 0,0 1,21 @@
# MIT License

Copyright (c) 2019 Bob Rudis

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

M NAMESPACE => NAMESPACE +9 -2
@@ 1,4 1,11 @@
# Generated by roxygen2: do not edit by hand

import(httr)
importFrom(jsonlite,fromJSON)
export(astronomical_twilight)
export(civil_twilight)
export(day_astronomical_twilight_length)
export(day_civil_twilight_length)
export(day_length)
export(day_nautical_twilight_length)
export(nautical_twilight)
export(sun_rise_set)
useDynLib(daybreak, .registration = TRUE)

M R/daybreak-package.R => R/daybreak-package.R +8 -4
@@ 1,9 1,13 @@
#' ...
#' 
#' Compute Sun Rise/Set Times, Start/End of Twilight, and the
#' Length of the Day at Any Date and Latitude
#'
#' A wrapper for Paul Schlyter's C-based library for computing
#' sunrise, sunset, twilight start and end, plus the length of day for
#' a given data and coordinates.
#'
#' @md
#' @name daybreak
#' @keywords internal
#' @author Bob Rudis (bob@@rud.is)
#' @import httr
#' @importFrom jsonlite fromJSON
#' @useDynLib daybreak, .registration = TRUE
"_PACKAGE"

A R/daybreak-wrappers.R => R/daybreak-wrappers.R +132 -0
@@ 0,0 1,132 @@
#' Length of day
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) length of day
#' @export
#' @examples
#' day_length("2019-12-31", -70.8636, 43.2683)
day_length <- function(date = Sys.Date(), lon, lat) {

  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)

  .Call("r_day_length", date$year+1900L, date$mon+1L, date$mday, lon, lat)

}


#' Length of civil twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) day civil twilight length
#' @export
#' @examples
#' day_length("2019-12-31", -70.8636, 43.2683)
day_civil_twilight_length <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_day_civil_twilight_length", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Length of nautical twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) day nautical twilight length
#' @export
#' @examples
#' day_nautical_twilight_length("2019-12-31", -70.8636, 43.2683)
day_nautical_twilight_length <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_day_nautical_twilight_length", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Length of astronomical twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) astronomical twilight length
#' @export
#' @examples
#' day_astronomical_twilight_length("2019-12-31", -70.8636, 43.2683)
day_astronomical_twilight_length <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_day_astronomical_twilight_length", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Sun rise/set times
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) sunrise/sunset
#' @export
#' @examples
#' sun_rise_set("2019-12-31", -70.8636, 43.2683)
sun_rise_set <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_sun_rise_set", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Civil twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) civil twilight
#' @export
#' @examples
#' civil_twilight("2019-12-31", -70.8636, 43.2683)
civil_twilight <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_civil_twilight", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Nautical twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) nautical twilight
#' @export
#' @examples
#' nautical_twilight("2019-12-31", -70.8636, 43.2683)
nautical_twilight <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_nautical_twilight", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}

#' Astronomical twilight
#'
#' @param date The date to compute the length for. An R [DateTimeClasses] object
#'     or something that can be coerced into one by [as.POSIXlt()].
#' @param lon,lat longitude & latitude
#' @return (dbl) astronomical twilight
#' @export
#' @examples
#' astronomical_twilight("2019-12-31", -70.8636, 43.2683)
astronomical_twilight <- function(date, lon, lat) {
  date <- valid_date(date)
  lon <- valid_lon(lon)
  lat <- valid_lat(lat)
  .Call("r_astronomical_twilight", date$year+1900L, date$mon+1L, date$mday, lon, lat)
}


A R/validators.R => R/validators.R +15 -0
@@ 0,0 1,15 @@
valid_date <- function(date) {
  as.POSIXlt(date[1])
}

valid_lon <- function(lon) {
  lon <- lon[1]
  stopifnot(lon >= -180 & lon <= 180)
  lon
}

valid_lat <- function(lat) {
  lat <- lat[1]
  stopifnot(lat >= -90 & lat <= 90)
  lat
}

M README.Rmd => README.Rmd +39 -0
@@ 39,6 39,45 @@ packageVersion("daybreak")

```

Near me:

```{r ex1}
day_length("2019-12-31", -70.8636, 43.2683)
day_civil_twilight_length("2019-12-31", -70.8636, 43.2683)
day_nautical_twilight_length("2019-12-31", -70.8636, 43.2683)
day_astronomical_twilight_length("2019-12-31", -70.8636, 43.2683)
sun_rise_set("2019-12-31", -70.8636, 43.2683)
civil_twilight("2019-12-31", -70.8636, 43.2683)
nautical_twilight("2019-12-31", -70.8636, 43.2683)
astronomical_twilight("2019-12-31", -70.8636, 43.2683)
```

Tromsø, Norway (Winter)

```{r ex2}
day_length("2019-12-31", 18.9553, 69.6492)
day_civil_twilight_length("2019-12-31", 18.9553, 69.6492)
day_nautical_twilight_length("2019-12-31", 18.9553, 69.6492)
day_astronomical_twilight_length("2019-12-31", 18.9553, 69.6492)
sun_rise_set("2019-12-31", 18.9553, 69.6492)
civil_twilight("2019-12-31", 18.9553, 69.6492)
nautical_twilight("2019-12-31", 18.9553, 69.6492)
astronomical_twilight("2019-12-31", 18.9553, 69.6492)
```

Tromsø, Norway (Summer)

```{r ex3}
day_length("2019-06-01", 18.9553, 69.6492)
day_civil_twilight_length("2019-06-01", 18.9553, 69.6492)
day_nautical_twilight_length("2019-06-01", 18.9553, 69.6492)
day_astronomical_twilight_length("2019-06-01", 18.9553, 69.6492)
sun_rise_set("2019-06-01", 18.9553, 69.6492)
civil_twilight("2019-06-01", 18.9553, 69.6492)
nautical_twilight("2019-06-01", 18.9553, 69.6492)
astronomical_twilight("2019-06-01", 18.9553, 69.6492)
```

## daybreak Metrics

```{r cloc, echo=FALSE}

A README.md => README.md +188 -0
@@ 0,0 1,188 @@

[![Project Status: Active – The project has reached a stable, usable
state and is being actively
developed.](https://www.repostatus.org/badges/latest/active.svg)](https://www.repostatus.org/#active)
[![Signed
by](https://img.shields.io/badge/Keybase-Verified-brightgreen.svg)](https://keybase.io/hrbrmstr)
![Signed commit
%](https://img.shields.io/badge/Signed_Commits-100%25-lightgrey.svg)
[![Linux build
Status](https://travis-ci.org/hrbrmstr/daybreak.svg?branch=master)](https://travis-ci.org/hrbrmstr/daybreak)  
![Minimal R
Version](https://img.shields.io/badge/R%3E%3D-3.2.0-blue.svg)
![License](https://img.shields.io/badge/License-MIT-blue.svg)

# daybreak

Compute Sun Rise/Set Times, Start/End of Twilight, and the Length of the
Day at Any Date and Latitude

## Description

A wrapper for Paul Schlyter’s C-based library for computing sunrise,
sunset, twilight start and end, plus the length of day for a given data
and coordinates.

## What’s Inside The Tin

The following functions are implemented:

  - `astronomical_twilight`: Astronomical twilight
  - `civil_twilight`: Civil twilight
  - `day_astronomical_twilight_length`: Length of astronomical twilight
  - `day_civil_twilight_length`: Length of civil twilight
  - `day_length`: Length of day
  - `day_nautical_twilight_length`: Length of nautical twilight
  - `nautical_twilight`: Nautical twilight
  - `sun_rise_set`: Sun rise/set times

## Installation

``` r
remotes::install_git("https://git.rud.is/hrbrmstr/daybreak.git")
# or
remotes::install_git("https://git.sr.ht/~hrbrmstr/daybreak")
# or
remotes::install_gitlab("hrbrmstr/daybreak")
# or
remotes::install_bitbucket("hrbrmstr/daybreak")
```

NOTE: To use the ‘remotes’ install options you will need to have the
[{remotes} package](https://github.com/r-lib/remotes) installed.

## Usage

``` r
library(daybreak)

# current version
packageVersion("daybreak")
## [1] '0.1.0'
```

Near me:

``` r
day_length("2019-12-31", -70.8636, 43.2683)
## [1] 9.031444
day_civil_twilight_length("2019-12-31", -70.8636, 43.2683)
## [1] 10.10834
day_nautical_twilight_length("2019-12-31", -70.8636, 43.2683)
## [1] 11.30569
day_astronomical_twilight_length("2019-12-31", -70.8636, 43.2683)
## [1] 12.45998
sun_rise_set("2019-12-31", -70.8636, 43.2683)
## $rise
## [1] 12.25761
## 
## $set
## [1] 21.28906
civil_twilight("2019-12-31", -70.8636, 43.2683)
## $start
## [1] 11.71917
## 
## $end
## [1] 21.82751
nautical_twilight("2019-12-31", -70.8636, 43.2683)
## $start
## [1] 11.12049
## 
## $end
## [1] 22.42618
astronomical_twilight("2019-12-31", -70.8636, 43.2683)
## $start
## [1] 10.54335
## 
## $end
## [1] 23.00332
```

Tromsø, Norway (Winter)

``` r
day_length("2019-12-31", 18.9553, 69.6492)
## [1] 0
day_civil_twilight_length("2019-12-31", 18.9553, 69.6492)
## [1] 4.613116
day_nautical_twilight_length("2019-12-31", 18.9553, 69.6492)
## [1] 8.000323
day_astronomical_twilight_length("2019-12-31", 18.9553, 69.6492)
## [1] 10.5871
sun_rise_set("2019-12-31", 18.9553, 69.6492)
## $rise
## [1] NA
## 
## $set
## [1] NA
civil_twilight("2019-12-31", 18.9553, 69.6492)
## $start
## [1] 8.476866
## 
## $end
## [1] 13.08998
nautical_twilight("2019-12-31", 18.9553, 69.6492)
## $start
## [1] 6.783262
## 
## $end
## [1] 14.78359
astronomical_twilight("2019-12-31", 18.9553, 69.6492)
## $start
## [1] 5.489872
## 
## $end
## [1] 16.07698
```

Tromsø, Norway (Summer)

``` r
day_length("2019-06-01", 18.9553, 69.6492)
## [1] 24
day_civil_twilight_length("2019-06-01", 18.9553, 69.6492)
## [1] 24
day_nautical_twilight_length("2019-06-01", 18.9553, 69.6492)
## [1] 24
day_astronomical_twilight_length("2019-06-01", 18.9553, 69.6492)
## [1] 24
sun_rise_set("2019-06-01", 18.9553, 69.6492)
## $rise
## [1] NA
## 
## $set
## [1] NA
civil_twilight("2019-06-01", 18.9553, 69.6492)
## $start
## [1] NA
## 
## $end
## [1] NA
nautical_twilight("2019-06-01", 18.9553, 69.6492)
## $start
## [1] NA
## 
## $end
## [1] NA
astronomical_twilight("2019-06-01", 18.9553, 69.6492)
## $start
## [1] NA
## 
## $end
## [1] NA
```

## daybreak Metrics

| Lang         | \# Files |  (%) | LoC |  (%) | Blank lines |  (%) | \# Lines |  (%) |
| :----------- | -------: | ---: | --: | ---: | ----------: | ---: | -------: | ---: |
| C            |        3 | 0.33 | 267 | 0.66 |         110 | 0.60 |      245 | 0.60 |
| R            |        4 | 0.44 |  65 | 0.16 |          16 | 0.09 |       84 | 0.20 |
| C/C++ Header |        1 | 0.11 |  39 | 0.10 |          35 | 0.19 |       44 | 0.11 |
| Rmd          |        1 | 0.11 |  32 | 0.08 |          21 | 0.12 |       37 | 0.09 |

## Code of Conduct

Please note that this project is released with a Contributor Code of
Conduct. By participating in this project you agree to abide by its
terms.

A inst/tinytest/test_daybreak.R => inst/tinytest/test_daybreak.R +119 -0
@@ 0,0 1,119 @@
expect_equivalent(
  day_length("2019-12-31", -70.8636, 43.2683),
  9.03144433072786
)

expect_equivalent(
  day_civil_twilight_length("2019-12-31", -70.8636, 43.2683),
  10.1083411766176
)

expect_equivalent(
  day_nautical_twilight_length("2019-12-31", -70.8636, 43.2683),
  11.3056891617088
)

expect_equivalent(
  day_astronomical_twilight_length("2019-12-31", -70.8636, 43.2683),
  12.459975565969
)

expect_equivalent(
  sun_rise_set("2019-12-31", -70.8636, 43.2683),
  list(rise = 12.2576146717076, set = 21.2890590024355)
)

expect_equivalent(
  civil_twilight("2019-12-31", -70.8636, 43.2683),
  list(start = 11.7191662487627, end = 21.8275074253803)
)

expect_equivalent(
  nautical_twilight("2019-12-31", -70.8636, 43.2683),
  list(start = 11.1204922562171, end = 22.4261814179259)
)

expect_equivalent(
  astronomical_twilight("2019-12-31", -70.8636, 43.2683),
  list(start = 10.543349054087, end = 23.003324620056)
)

expect_equivalent(
  day_length("2019-12-31", 18.9553, 69.6492),
  0
)

expect_equivalent(
  day_civil_twilight_length("2019-12-31", 18.9553, 69.6492),
  4.61311561714866
)

expect_equivalent(
  day_nautical_twilight_length("2019-12-31", 18.9553, 69.6492),
  8.00032348106164
)

expect_equivalent(
  day_astronomical_twilight_length("2019-12-31", 18.9553, 69.6492),
  10.5871031550164
)

expect_equivalent(
  sun_rise_set("2019-12-31", 18.9553, 69.6492),
  list(rise = NA_real_, set = NA_real_)
)

expect_equivalent(
  civil_twilight("2019-12-31", 18.9553, 69.6492),
  list(start = 8.47686578254252, end = 13.0899813996912)
)

expect_equivalent(
  nautical_twilight("2019-12-31", 18.9553, 69.6492),
  list(start = 6.78326185058603, end = 14.7835853316477)
)

expect_equivalent(
  astronomical_twilight("2019-12-31", 18.9553, 69.6492),
  list(start = 5.48987201360863, end = 16.0769751686251)
)

expect_equivalent(
  day_length("2019-06-01", 18.9553, 69.6492),
  24
)

expect_equivalent(
  day_civil_twilight_length("2019-06-01", 18.9553, 69.6492),
  24
)

expect_equivalent(
  day_nautical_twilight_length("2019-06-01", 18.9553, 69.6492),
  24
)

expect_equivalent(
  day_astronomical_twilight_length("2019-06-01", 18.9553, 69.6492),
  24
)

expect_equivalent(
  sun_rise_set("2019-06-01", 18.9553, 69.6492),
  list(rise = NA_real_, set = NA_real_)
)

expect_equivalent(
  civil_twilight("2019-06-01", 18.9553, 69.6492),
  list(start = NA_real_, end = NA_real_)
)

expect_equivalent(
  nautical_twilight("2019-06-01", 18.9553, 69.6492),
  list(start = NA_real_, end = NA_real_)
)

expect_equivalent(
  astronomical_twilight("2019-06-01", 18.9553, 69.6492),
  list(start = NA_real_, end = NA_real_)
)

A man/astronomical_twilight.Rd => man/astronomical_twilight.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{astronomical_twilight}
\alias{astronomical_twilight}
\title{Astronomical twilight}
\usage{
astronomical_twilight(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) astronomical twilight
}
\description{
Astronomical twilight
}
\examples{
astronomical_twilight("2019-12-31", -70.8636, 43.2683)
}

A man/civil_twilight.Rd => man/civil_twilight.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{civil_twilight}
\alias{civil_twilight}
\title{Civil twilight}
\usage{
civil_twilight(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) civil twilight
}
\description{
Civil twilight
}
\examples{
civil_twilight("2019-12-31", -70.8636, 43.2683)
}

A man/day_astronomical_twilight_length.Rd => man/day_astronomical_twilight_length.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{day_astronomical_twilight_length}
\alias{day_astronomical_twilight_length}
\title{Length of astronomical twilight}
\usage{
day_astronomical_twilight_length(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) astronomical twilight length
}
\description{
Length of astronomical twilight
}
\examples{
day_astronomical_twilight_length("2019-12-31", -70.8636, 43.2683)
}

A man/day_civil_twilight_length.Rd => man/day_civil_twilight_length.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{day_civil_twilight_length}
\alias{day_civil_twilight_length}
\title{Length of civil twilight}
\usage{
day_civil_twilight_length(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) day civil twilight length
}
\description{
Length of civil twilight
}
\examples{
day_length("2019-12-31", -70.8636, 43.2683)
}

A man/day_length.Rd => man/day_length.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{day_length}
\alias{day_length}
\title{Length of day}
\usage{
day_length(date = Sys.Date(), lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) length of day
}
\description{
Length of day
}
\examples{
day_length("2019-12-31", -70.8636, 43.2683)
}

A man/day_nautical_twilight_length.Rd => man/day_nautical_twilight_length.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{day_nautical_twilight_length}
\alias{day_nautical_twilight_length}
\title{Length of nautical twilight}
\usage{
day_nautical_twilight_length(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) day nautical twilight length
}
\description{
Length of nautical twilight
}
\examples{
day_nautical_twilight_length("2019-12-31", -70.8636, 43.2683)
}

M man/daybreak.Rd => man/daybreak.Rd +5 -2
@@ 4,9 4,12 @@
\name{daybreak}
\alias{daybreak}
\alias{daybreak-package}
\title{...}
\title{Compute Sun Rise/Set Times, Start/End of Twilight, and the
Length of the Day at Any Date and Latitude}
\description{
A good description goes here otherwise CRAN checks fail.
A wrapper for Paul Schlyter's C-based library for computing
sunrise, sunset, twilight start and end, plus the length of day for
a given data and coordinates.
}
\seealso{
Useful links:

A man/nautical_twilight.Rd => man/nautical_twilight.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{nautical_twilight}
\alias{nautical_twilight}
\title{Nautical twilight}
\usage{
nautical_twilight(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) nautical twilight
}
\description{
Nautical twilight
}
\examples{
nautical_twilight("2019-12-31", -70.8636, 43.2683)
}

A man/sun_rise_set.Rd => man/sun_rise_set.Rd +23 -0
@@ 0,0 1,23 @@
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/daybreak-wrappers.R
\name{sun_rise_set}
\alias{sun_rise_set}
\title{Sun rise/set times}
\usage{
sun_rise_set(date, lon, lat)
}
\arguments{
\item{date}{The date to compute the length for. An R \link{DateTimeClasses} object
or something that can be coerced into one by \code{\link[=as.POSIXlt]{as.POSIXlt()}}.}

\item{lon, lat}{longitude & latitude}
}
\value{
(dbl) sunrise/sunset
}
\description{
Sun rise/set times
}
\examples{
sun_rise_set("2019-12-31", -70.8636, 43.2683)
}

A src/daybreak-main.c => src/daybreak-main.c +176 -0
@@ 0,0 1,176 @@
#include <R.h>
#include <Rinternals.h>

#include "sunriset.h"

SEXP r_day_length(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  SEXP out = PROTECT(allocVector(REALSXP, 1));
  REAL(out)[0] = day_length(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat)
  );
  UNPROTECT(1);

  return(out);

}

SEXP r_day_civil_twilight_length(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  SEXP out = PROTECT(allocVector(REALSXP, 1));
  REAL(out)[0] = day_civil_twilight_length(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat)
  );
  UNPROTECT(1);

  return(out);

}

SEXP r_day_nautical_twilight_length(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  SEXP out = PROTECT(allocVector(REALSXP, 1));
  REAL(out)[0] = day_nautical_twilight_length(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat)
  );
  UNPROTECT(1);

  return(out);

}

SEXP r_day_astronomical_twilight_length(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  SEXP out = PROTECT(allocVector(REALSXP, 1));
  REAL(out)[0] = day_astronomical_twilight_length(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat)
  );
  UNPROTECT(1);

  return(out);

}

SEXP r_sun_rise_set(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  double rise, set;

  int res = sun_rise_set(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat),
    &rise, &set
  );

  const char *names[] = {
    "rise",
    "set",
    ""
  };

  SEXP out = PROTECT(mkNamed(VECSXP, names));

  if (res == 0) {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(rise)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(set)));
  } else {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(NA_REAL)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(NA_REAL)));
  }

  UNPROTECT(3);

  return(out);

}

SEXP r_civil_twilight(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  double start, end;

  int res = civil_twilight(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat),
    &start, &end
  );

  const char *names[] = {
    "start",
    "end",
    ""
  };

  SEXP out = PROTECT(mkNamed(VECSXP, names));

  if (res == 0) {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(start)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(end)));
  } else {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(NA_REAL)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(NA_REAL)));
  }

  UNPROTECT(3);

  return(out);

}

SEXP r_nautical_twilight(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  double start, end;

  int res = nautical_twilight(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat),
    &start, &end
  );

  const char *names[] = {
    "start",
    "end",
    ""
  };

  SEXP out = PROTECT(mkNamed(VECSXP, names));

  if (res == 0) {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(start)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(end)));
  } else {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(NA_REAL)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(NA_REAL)));
  }

  UNPROTECT(3);

  return(out);

}

SEXP r_astronomical_twilight(SEXP year, SEXP month, SEXP day, SEXP lon, SEXP lat) {

  double start, end;

  int res = astronomical_twilight(
    asInteger(year), asInteger(month), asInteger(day), asReal(lon), asReal(lat),
    &start, &end
  );

  const char *names[] = {
    "start",
    "end",
    ""
  };

  SEXP out = PROTECT(mkNamed(VECSXP, names));

  if (res == 0) {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(start)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(end)));
  } else {
    SET_VECTOR_ELT(out, 0, PROTECT(ScalarReal(NA_REAL)));
    SET_VECTOR_ELT(out, 1, PROTECT(ScalarReal(NA_REAL)));
  }

  UNPROTECT(3);

  return(out);

}

A src/init.c => src/init.c +32 -0
@@ 0,0 1,32 @@
#include <R.h>
#include <Rinternals.h>
#include <stdlib.h> // for NULL
#include <R_ext/Rdynload.h>

/* .Call calls */
extern SEXP r_astronomical_twilight(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_civil_twilight(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_day_astronomical_twilight_length(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_day_civil_twilight_length(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_day_length(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_day_nautical_twilight_length(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_nautical_twilight(SEXP, SEXP, SEXP, SEXP, SEXP);
extern SEXP r_sun_rise_set(SEXP, SEXP, SEXP, SEXP, SEXP);

static const R_CallMethodDef CallEntries[] = {
    {"r_astronomical_twilight",            (DL_FUNC) &r_astronomical_twilight,            5},
    {"r_civil_twilight",                   (DL_FUNC) &r_civil_twilight,                   5},
    {"r_day_astronomical_twilight_length", (DL_FUNC) &r_day_astronomical_twilight_length, 5},
    {"r_day_civil_twilight_length",        (DL_FUNC) &r_day_civil_twilight_length,        5},
    {"r_day_length",                       (DL_FUNC) &r_day_length,                       5},
    {"r_day_nautical_twilight_length",     (DL_FUNC) &r_day_nautical_twilight_length,     5},
    {"r_nautical_twilight",                (DL_FUNC) &r_nautical_twilight,                5},
    {"r_sun_rise_set",                     (DL_FUNC) &r_sun_rise_set,                     5},
    {NULL, NULL, 0}
};

void R_init_daybreak(DllInfo *dll)
{
    R_registerRoutines(dll, NULL, CallEntries, NULL, NULL);
    R_useDynamicSymbols(dll, FALSE);
}

A src/sunriset.c => src/sunriset.c +414 -0
@@ 0,0 1,414 @@
/* +++Date last modified: 05-Jul-1997 */
/* Updated comments, 05-Aug-2013 */

/*

SUNRISET.C - computes Sun rise/set times, start/end of twilight, and
             the length of the day at any date and latitude

Written as DAYLEN.C, 1989-08-16

Modified to SUNRISET.C, 1992-12-01
Split to a header file, 2017-12-10, by Joachim Nilsson

(c) Paul Schlyter, 1989, 1992

Released to the public domain by Paul Schlyter, December 1992

*/

#include <stdio.h>
#include <math.h>

#include "sunriset.h"

/* A small test program */
// #ifndef SUNRISET_LIB
// int main(void)
// {
//       int year,month,day;
//       double lon, lat;
//       double daylen, civlen, nautlen, astrlen;
//       double rise, set, civ_start, civ_end, naut_start, naut_end,
//              astr_start, astr_end;
//       int    rs‘, civ, naut, astr;
//       char buf[80];
//
//       printf( "Latitude (+ is north) and longitude (+ is east) : " );
//       fgets(buf, 80, stdin);
//       sscanf(buf, "%lf %lf", &lat, &lon );
//
//       for(;;)
//       {
//             printf( "Input date ( yyyy mm dd ) (ctrl-C exits): " );
//             fgets(buf, 80, stdin);
//             sscanf(buf, "%d %d %d", &year, &month, &day );
//
//             daylen  = day_length(year,month,day,lon,lat);
//             civlen  = day_civil_twilight_length(year,month,day,lon,lat);
//             nautlen = day_nautical_twilight_length(year,month,day,lon,lat);
//             astrlen = day_astronomical_twilight_length(year,month,day,
//                   lon,lat);
//
//             printf( "Day length:                 %5.2f hours\n", daylen );
//             printf( "With civil twilight         %5.2f hours\n", civlen );
//             printf( "With nautical twilight      %5.2f hours\n", nautlen );
//             printf( "With astronomical twilight  %5.2f hours\n", astrlen );
//             printf( "Length of twilight: civil   %5.2f hours\n",
//                   (civlen-daylen)/2.0);
//             printf( "                  nautical  %5.2f hours\n",
//                   (nautlen-daylen)/2.0);
//             printf( "              astronomical  %5.2f hours\n",
//                   (astrlen-daylen)/2.0);
//
//             rs   = sun_rise_set         ( year, month, day, lon, lat,
//                                           &rise, &set );
//             civ  = civil_twilight       ( year, month, day, lon, lat,
//                                           &civ_start, &civ_end );
//             naut = nautical_twilight    ( year, month, day, lon, lat,
//                                           &naut_start, &naut_end );
//             astr = astronomical_twilight( year, month, day, lon, lat,
//                                           &astr_start, &astr_end );
//
//             printf( "Sun at south %5.2fh UT\n", (rise+set)/2.0 );
//
//             switch( rs )
//             {
//                 case 0:
//                     printf( "Sun rises %5.2fh UT, sets %5.2fh UT\n",
//                              rise, set );
//                     break;
//                 case +1:
//                     printf( "Sun above horizon\n" );
//                     break;
//                 case -1:
//                     printf( "Sun below horizon\n" );
//                     break;
//             }
//
//             switch( civ )
//             {
//                 case 0:
//                     printf( "Civil twilight starts %5.2fh, "
//                             "ends %5.2fh UT\n", civ_start, civ_end );
//                     break;
//                 case +1:
//                     printf( "Never darker than civil twilight\n" );
//                     break;
//                 case -1:
//                     printf( "Never as bright as civil twilight\n" );
//                     break;
//             }
//
//             switch( naut )
//             {
//                 case 0:
//                     printf( "Nautical twilight starts %5.2fh, "
//                             "ends %5.2fh UT\n", naut_start, naut_end );
//                     break;
//                 case +1:
//                     printf( "Never darker than nautical twilight\n" );
//                     break;
//                 case -1:
//                     printf( "Never as bright as nautical twilight\n" );
//                     break;
//             }
//
//             switch( astr )
//             {
//                 case 0:
//                     printf( "Astronomical twilight starts %5.2fh, "
//                             "ends %5.2fh UT\n", astr_start, astr_end );
//                     break;
//                 case +1:
//                     printf( "Never darker than astronomical twilight\n" );
//                     break;
//                 case -1:
//                     printf( "Never as bright as astronomical twilight\n" );
//                     break;
//             }
//       return 0;
//       }
// }
// #endif /* SUNRISET_LIB */

/* The "workhorse" function for sun rise/set times */

int __sunriset__( int year, int month, int day, double lon, double lat,
                  double altit, int upper_limb, double *trise, double *tset )
/***************************************************************************/
/* Note: year,month,date = calendar date, 1801-2099 only.             */
/*       Eastern longitude positive, Western longitude negative       */
/*       Northern latitude positive, Southern latitude negative       */
/*       The longitude value IS critical in this function!            */
/*       altit = the altitude which the Sun should cross              */
/*               Set to -35/60 degrees for rise/set, -6 degrees       */
/*               for civil, -12 degrees for nautical and -18          */
/*               degrees for astronomical twilight.                   */
/*         upper_limb: non-zero -> upper limb, zero -> center         */
/*               Set to non-zero (e.g. 1) when computing rise/set     */
/*               times, and to zero when computing start/end of       */
/*               twilight.                                            */
/*        *rise = where to store the rise time                        */
/*        *set  = where to store the set  time                        */
/*                Both times are relative to the specified altitude,  */
/*                and thus this function can be used to compute       */
/*                various twilight times, as well as rise/set times   */
/* Return value:  0 = sun rises/sets this day, times stored at        */
/*                    *trise and *tset.                               */
/*               +1 = sun above the specified "horizon" 24 hours.     */
/*                    *trise set to time when the sun is at south,    */
/*                    minus 12 hours while *tset is set to the south  */
/*                    time plus 12 hours. "Day" length = 24 hours     */
/*               -1 = sun is below the specified "horizon" 24 hours   */
/*                    "Day" length = 0 hours, *trise and *tset are    */
/*                    both set to the time when the sun is at south.  */
/*                                                                    */
/**********************************************************************/
{
      double  d,  /* Days since 2000 Jan 0.0 (negative before) */
      sr,         /* Solar distance, astronomical units */
      sRA,        /* Sun's Right Ascension */
      sdec,       /* Sun's declination */
      sradius,    /* Sun's apparent radius */
      t,          /* Diurnal arc */
      tsouth,     /* Time when Sun is at south */
      sidtime;    /* Local sidereal time */

      int rc = 0; /* Return cde from function - usually 0 */

      /* Compute d of 12h local mean solar time */
      d = days_since_2000_Jan_0(year,month,day) + 0.5 - lon/360.0;

      /* Compute the local sidereal time of this moment */
      sidtime = revolution( GMST0(d) + 180.0 + lon );

      /* Compute Sun's RA, Decl and distance at this moment */
      sun_RA_dec( d, &sRA, &sdec, &sr );

      /* Compute time when Sun is at south - in hours UT */
      tsouth = 12.0 - rev180(sidtime - sRA)/15.0;

      /* Compute the Sun's apparent radius in degrees */
      sradius = 0.2666 / sr;

      /* Do correction to upper limb, if necessary */
      if ( upper_limb )
            altit -= sradius;

      /* Compute the diurnal arc that the Sun traverses to reach */
      /* the specified altitude altit: */
      {
            double cost;
            cost = ( sind(altit) - sind(lat) * sind(sdec) ) /
                  ( cosd(lat) * cosd(sdec) );
            if ( cost >= 1.0 )
                  rc = -1, t = 0.0;       /* Sun always below altit */
            else if ( cost <= -1.0 )
                  rc = +1, t = 12.0;      /* Sun always above altit */
            else
                  t = acosd(cost)/15.0;   /* The diurnal arc, hours */
      }

      /* Store rise and set times - in hours UT */
      *trise = tsouth - t;
      *tset  = tsouth + t;

      return rc;
}  /* __sunriset__ */



/* The "workhorse" function */


double __daylen__( int year, int month, int day, double lon, double lat,
                   double altit, int upper_limb )
/**********************************************************************/
/* Note: year,month,date = calendar date, 1801-2099 only.             */
/*       Eastern longitude positive, Western longitude negative       */
/*       Northern latitude positive, Southern latitude negative       */
/*       The longitude value is not critical. Set it to the correct   */
/*       longitude if you're picky, otherwise set to to, say, 0.0     */
/*       The latitude however IS critical - be sure to get it correct */
/*       altit = the altitude which the Sun should cross              */
/*               Set to -35/60 degrees for rise/set, -6 degrees       */
/*               for civil, -12 degrees for nautical and -18          */
/*               degrees for astronomical twilight.                   */
/*         upper_limb: non-zero -> upper limb, zero -> center         */
/*               Set to non-zero (e.g. 1) when computing day length   */
/*               and to zero when computing day+twilight length.      */
/**********************************************************************/
{
      double  d,  /* Days since 2000 Jan 0.0 (negative before) */
      obl_ecl,    /* Obliquity (inclination) of Earth's axis */
      sr,         /* Solar distance, astronomical units */
      slon,       /* True solar longitude */
      sin_sdecl,  /* Sine of Sun's declination */
      cos_sdecl,  /* Cosine of Sun's declination */
      sradius,    /* Sun's apparent radius */
      t;          /* Diurnal arc */

      /* Compute d of 12h local mean solar time */
      d = days_since_2000_Jan_0(year,month,day) + 0.5 - lon/360.0;

      /* Compute obliquity of ecliptic (inclination of Earth's axis) */
      obl_ecl = 23.4393 - 3.563E-7 * d;

      /* Compute Sun's ecliptic longitude and distance */
      sunpos( d, &slon, &sr );

      /* Compute sine and cosine of Sun's declination */
      sin_sdecl = sind(obl_ecl) * sind(slon);
      cos_sdecl = sqrt( 1.0 - sin_sdecl * sin_sdecl );

      /* Compute the Sun's apparent radius, degrees */
      sradius = 0.2666 / sr;

      /* Do correction to upper limb, if necessary */
      if ( upper_limb )
            altit -= sradius;

      /* Compute the diurnal arc that the Sun traverses to reach */
      /* the specified altitude altit: */
      {
            double cost;
            cost = ( sind(altit) - sind(lat) * sin_sdecl ) /
                  ( cosd(lat) * cos_sdecl );
            if ( cost >= 1.0 )
                  t = 0.0;                      /* Sun always below altit */
            else if ( cost <= -1.0 )
                  t = 24.0;                     /* Sun always above altit */
            else  t = (2.0/15.0) * acosd(cost); /* The diurnal arc, hours */
      }
      return t;
}  /* __daylen__ */


/* This function computes the Sun's position at any instant */

void sunpos( double d, double *lon, double *r )
/******************************************************/
/* Computes the Sun's ecliptic longitude and distance */
/* at an instant given in d, number of days since     */
/* 2000 Jan 0.0.  The Sun's ecliptic latitude is not  */
/* computed, since it's always very near 0.           */
/******************************************************/
{
      double M,         /* Mean anomaly of the Sun */
             w,         /* Mean longitude of perihelion */
                        /* Note: Sun's mean longitude = M + w */
             e,         /* Eccentricity of Earth's orbit */
             E,         /* Eccentric anomaly */
             x, y,      /* x, y coordinates in orbit */
             v;         /* True anomaly */

      /* Compute mean elements */
      M = revolution( 356.0470 + 0.9856002585 * d );
      w = 282.9404 + 4.70935E-5 * d;
      e = 0.016709 - 1.151E-9 * d;

      /* Compute true longitude and radius vector */
      E = M + e * RADEG * sind(M) * ( 1.0 + e * cosd(M) );
            x = cosd(E) - e;
      y = sqrt( 1.0 - e*e ) * sind(E);
      *r = sqrt( x*x + y*y );              /* Solar distance */
      v = atan2d( y, x );                  /* True anomaly */
      *lon = v + w;                        /* True solar longitude */
      if ( *lon >= 360.0 )
            *lon -= 360.0;                   /* Make it 0..360 degrees */
}

void sun_RA_dec( double d, double *RA, double *dec, double *r )
/******************************************************/
/* Computes the Sun's equatorial coordinates RA, Decl */
/* and also its distance, at an instant given in d,   */
/* the number of days since 2000 Jan 0.0.             */
/******************************************************/
{
      double lon, obl_ecl, x, y, z;

      /* Compute Sun's ecliptical coordinates */
      sunpos( d, &lon, r );

      /* Compute ecliptic rectangular coordinates (z=0) */
      x = *r * cosd(lon);
      y = *r * sind(lon);

      /* Compute obliquity of ecliptic (inclination of Earth's axis) */
      obl_ecl = 23.4393 - 3.563E-7 * d;

      /* Convert to equatorial rectangular coordinates - x is unchanged */
      z = y * sind(obl_ecl);
      y = y * cosd(obl_ecl);

      /* Convert to spherical coordinates */
      *RA = atan2d( y, x );
      *dec = atan2d( z, sqrt(x*x + y*y) );

}  /* sun_RA_dec */


/******************************************************************/
/* This function reduces any angle to within the first revolution */
/* by subtracting or adding even multiples of 360.0 until the     */
/* result is >= 0.0 and < 360.0                                   */
/******************************************************************/

#define INV360    ( 1.0 / 360.0 )

double revolution( double x )
/*****************************************/
/* Reduce angle to within 0..360 degrees */
/*****************************************/
{
      return( x - 360.0 * floor( x * INV360 ) );
}  /* revolution */

double rev180( double x )
/*********************************************/
/* Reduce angle to within +180..+180 degrees */
/*********************************************/
{
      return( x - 360.0 * floor( x * INV360 + 0.5 ) );
}  /* revolution */


/*******************************************************************/
/* This function computes GMST0, the Greenwich Mean Sidereal Time  */
/* at 0h UT (i.e. the sidereal time at the Greenwich meridian at   */
/* 0h UT).  GMST is then the sidereal time at Greenwich at any     */
/* time of the day.  I've generalized GMST0 as well, and define it */
/* as:  GMST0 = GMST - UT  --  this allows GMST0 to be computed at */
/* other times than 0h UT as well.  While this sounds somewhat     */
/* contradictory, it is very practical:  instead of computing      */
/* GMST like:                                                      */
/*                                                                 */
/*  GMST = (GMST0) + UT * (366.2422/365.2422)                      */
/*                                                                 */
/* where (GMST0) is the GMST last time UT was 0 hours, one simply  */
/* computes:                                                       */
/*                                                                 */
/*  GMST = GMST0 + UT                                              */
/*                                                                 */
/* where GMST0 is the GMST "at 0h UT" but at the current moment!   */
/* Defined in this way, GMST0 will increase with about 4 min a     */
/* day.  It also happens that GMST0 (in degrees, 1 hr = 15 degr)   */
/* is equal to the Sun's mean longitude plus/minus 180 degrees!    */
/* (if we neglect aberration, which amounts to 20 seconds of arc   */
/* or 1.33 seconds of time)                                        */
/*                                                                 */
/*******************************************************************/

double GMST0( double d )
{
      double sidtim0;
      /* Sidtime at 0h UT = L (Sun's mean longitude) + 180.0 degr  */
      /* L = M + w, as defined in sunpos().  Since I'm too lazy to */
      /* add these numbers, I'll let the C compiler do it for me.  */
      /* Any decent C compiler will add the constants at compile   */
      /* time, imposing no runtime or code overhead.               */
      sidtim0 = revolution( ( 180.0 + 356.0470 + 282.9404 ) +
                          ( 0.9856002585 + 4.70935E-5 ) * d );
      return sidtim0;
}  /* GMST0 */
\ No newline at end of file

A src/sunriset.h => src/sunriset.h +118 -0
@@ 0,0 1,118 @@
/*

SUNRISET.H - computes Sun rise/set times, start/end of twilight, and
             the length of the day at any date and latitude

Written as DAYLEN.C, 1989-08-16

Modified to SUNRISET.C, 1992-12-01
Split to a header file, 2017-12-10, by Joachim Nilsson

(c) Paul Schlyter, 1989, 1992

Released to the public domain by Paul Schlyter, December 1992

*/

/* A macro to compute the number of days elapsed since 2000 Jan 0.0 */
/* (which is equal to 1999 Dec 31, 0h UT)                           */

#define days_since_2000_Jan_0(y,m,d) \
    (367L*(y)-((7*((y)+(((m)+9)/12)))/4)+((275*(m))/9)+(d)-730530L)

/* Some conversion factors between radians and degrees */

#ifndef PI
 #define PI        3.1415926535897932384
#endif

#define RADEG     ( 180.0 / PI )
#define DEGRAD    ( PI / 180.0 )

/* The trigonometric functions in degrees */

#define sind(x)  sin((x)*DEGRAD)
#define cosd(x)  cos((x)*DEGRAD)
#define tand(x)  tan((x)*DEGRAD)

#define atand(x)    (RADEG*atan(x))
#define asind(x)    (RADEG*asin(x))
#define acosd(x)    (RADEG*acos(x))
#define atan2d(y,x) (RADEG*atan2(y,x))


/* Following are some macros around the "workhorse" function __daylen__ */
/* They mainly fill in the desired values for the reference altitude    */
/* below the horizon, and also selects whether this altitude should     */
/* refer to the Sun's center or its upper limb.                         */


/* This macro computes the length of the day, from sunrise to sunset. */
/* Sunrise/set is considered to occur when the Sun's upper limb is    */
/* 35 arc minutes below the horizon (this accounts for the refraction */
/* of the Earth's atmosphere).                                        */
#define day_length(year,month,day,lon,lat)  \
        __daylen__( year, month, day, lon, lat, -35.0/60.0, 1 )

/* This macro computes the length of the day, including civil twilight. */
/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
/* the horizon.                                                         */
#define day_civil_twilight_length(year,month,day,lon,lat)  \
        __daylen__( year, month, day, lon, lat, -6.0, 0 )

/* This macro computes the length of the day, incl. nautical twilight.  */
/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
/* below the horizon.                                                   */
#define day_nautical_twilight_length(year,month,day,lon,lat)  \
        __daylen__( year, month, day, lon, lat, -12.0, 0 )

/* This macro computes the length of the day, incl. astronomical twilight. */
/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
/* below the horizon.                                                      */
#define day_astronomical_twilight_length(year,month,day,lon,lat)  \
        __daylen__( year, month, day, lon, lat, -18.0, 0 )


/* This macro computes times for sunrise/sunset.                      */
/* Sunrise/set is considered to occur when the Sun's upper limb is    */
/* 35 arc minutes below the horizon (this accounts for the refraction */
/* of the Earth's atmosphere).                                        */
#define sun_rise_set(year,month,day,lon,lat,rise,set)  \
        __sunriset__( year, month, day, lon, lat, -35.0/60.0, 1, rise, set )

/* This macro computes the start and end times of civil twilight.       */
/* Civil twilight starts/ends when the Sun's center is 6 degrees below  */
/* the horizon.                                                         */
#define civil_twilight(year,month,day,lon,lat,start,end)  \
        __sunriset__( year, month, day, lon, lat, -6.0, 0, start, end )

/* This macro computes the start and end times of nautical twilight.    */
/* Nautical twilight starts/ends when the Sun's center is 12 degrees    */
/* below the horizon.                                                   */
#define nautical_twilight(year,month,day,lon,lat,start,end)  \
        __sunriset__( year, month, day, lon, lat, -12.0, 0, start, end )

/* This macro computes the start and end times of astronomical twilight.   */
/* Astronomical twilight starts/ends when the Sun's center is 18 degrees   */
/* below the horizon.                                                      */
#define astronomical_twilight(year,month,day,lon,lat,start,end)  \
        __sunriset__( year, month, day, lon, lat, -18.0, 0, start, end )


/* Function prototypes */

double __daylen__( int year, int month, int day, double lon, double lat,
                   double altit, int upper_limb );

int __sunriset__( int year, int month, int day, double lon, double lat,
                  double altit, int upper_limb, double *rise, double *set );

void sunpos( double d, double *lon, double *r );

void sun_RA_dec( double d, double *RA, double *dec, double *r );

double revolution( double x );

double rev180( double x );

double GMST0( double d );

A tests/tinytest.R => tests/tinytest.R +5 -0
@@ 0,0 1,5 @@

if ( requireNamespace("tinytest", quietly=TRUE) ){
  tinytest::test_package("daybreak")
}