R/deg.dist.r

In wrbrooks/gwselect: Variable selection in Geographically Weighted Regression models

deg.dist = function (long1, lat1, long2, lat2) {
    rad <- pi/180
    a1 <- lat1 * rad
    a2 <- long1 * rad
    b1 <- lat2 * rad
    b2 <- long2 * rad
    dlon <- b2 - a2
    dlat <- b1 - a1
    a <- (sin(dlat/2))^2 + cos(a1) * cos(b1) * (sin(dlon/2))^2
    c <- 2 * atan2(sqrt(a), sqrt(1 - a))
    R <- 40041.47/(2 * pi)
    d <- R * c
    return(d)
}