Calculate day length

daylength.R

#'@references \url{http://aa.usno.navy.mil/data/docs/RS_OneYear.php}
#'@return A 3 x 365 data.frame of sunrise, sunset, date where times are in GMT
#'@examples \dontrun{
#' sunsetrise_yr(year = 2015, lon_deg = 80, lon_min = 26, lat_deg = 25, lat_min = 5, tz = 5)
#' }

sunsetrise_yr <- function(year, lon_sign = -1, lon_deg, lon_min, lat_sign = 1, lat_deg, lat_min, tz, tz_sign = 1){
  
  url <- "http://aa.usno.navy.mil"
  
  query <-   list(
              ID = "JS",
              year = year,
              task = 0,
              lon_sign = lon_sign,
              lon_deg = lon_deg,
              lon_min = lon_min,
              lat_sign = lat_sign,
              lat_deg = lat_deg,
              lat_min = lat_min,
              tz = tz, 
              tz_sign = tz_sign)
  
  rs <- httr::GET(url, path = "cgi-bin/aa_rstablew.pl", query = query)

  strsplit(httr::content(rs, "text"), "\n")[[1]][19:62]
} 
 

This function and associated functions moved to a package at: https://github.com/jsta/twilight