R function to convert degrees to radians

December 23, 2010
By

(This article was first published on Fabio Marroni's Blog » R, and kindly contributed to R-bloggers)

I would have never imagined that I would have to go back to high school concepts and do strange trigonometric calculations.

However, it happened to me that I needed to convert GPS coordinates of a large data set to radians. It’s a trivial task, if you know how to do it.

The function takes as input two numbers: degrees and minutes (no seconds for the moment, sorry!), converts it in decimal form of degrees and then return a numeric value, which represents your coordinate in radiants.

As, usual, comments welcome.

degrees.to.radians<-function(degrees=45,minutes=30)
{
if(!is.numeric(minutes)) stop("Please enter a numeric value for minutes!\n")
if(!is.numeric(degrees)) stop("Please enter a numeric value for degrees!\n")
decimal<-minutes/60
c.num<-degrees+decimal
radians<-c.num*pi/180
radians
}

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