Figuring out a locations local daylight hours

the maptools library in R can take care of this easily. Look for the 
sunriset function. You can get hours of daylight based on times of 
sunrise and sunset, and adjust according to whatever type of twilight 
definition you wish (i.e. civil vs. astronomical)

hope that helps

Ben

------ Original Message ------
From: "steven brey" <fierceturtle at gmail.com>
To: r-sig-geo at r-project.org
Sent: 5/20/2014 3:19:23 PM
Subject: [R-sig-Geo] Figuring out a locations local daylight hours

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

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