Calculate declination angle as in Yard et al. (2005)

Usage

calc_declination_angle(jday, format = c("degrees", "radians"))

Arguments

jday: The day of year as a number between 0 (Jan 1) and 364 (365 also OK for leap year)
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 declination angle corresponding to each value supplied in

jday.

References

Yard, Michael D., Glenn E. Bennett, Steve N. Mietz, Lewis G. Coggins Jr., Lawrence E. Stevens, Susan Hueftle, and Dean W. Blinn. Influence of Topographic Complexity on Solar Insolation Estimates for the Colorado River, Grand Canyon, AZ. Ecological Modelling 183, no. 2-3 (April 25, 2005): 157-72. doi:10.1016/j.ecolmodel.2004.07.027.

Examples

decdf <- data.frame(jday=1:366,
  dec=streamMetabolizer:::calc_declination_angle(1:366))
if (FALSE) {
library(ggplot2)
ggplot(unitted::v(decdf), aes(x=jday, y=dec)) + geom_line()
}