Calculate hour angle as in http://education.gsfc.nasa.gov/experimental/July61999siteupdate/inv99Project.Site/Pages/solar.insolation.html.

This is an approximation when hour is in clock time; should actually be given in solar time

Usage

calc_hour_angle(hour, format = c("degrees", "radians"))

Arguments

hour

numeric value or vector. hour since [solar] midnight as number between 0 and 23.999

format

The format of both the input and the output. May be "degrees" or "radians".

Value

numeric value or vector, in the units specified by format, indicating the angle corresponding to each value supplied in hour.

Examples

hourdf <- data.frame(hour=c(0:12,12.5:23.5),
  hragl=streamMetabolizer:::calc_hour_angle(c(0:12,12.5:23.5)))
if (FALSE) {
library(ggplot2)
ggplot(hourdf, aes(x=hour, y=hragl)) +
  geom_hline(yintercept=0, color="gold") + geom_line()
}