[R-sig-Geo] Figuring out a locations local daylight hours

[steven brey]

I am using R to write a text forecast for particulate matter
concentrations. Given a date, latitude, and longitude I would like to
figure out the local daylight hours. Does anyone know of a resource
that can make this calculation? I wanted to see if there was an
existing resource/solution before diving into the
trigonometry/astronomy 101 necessary to figure this out.

Cheers