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delta_itm
2012 Apr 08
0
multithreaded low level functions
...X),length(vecY)))
#print(sprintf("Len delta_lon: %d", length(delta_lon)))
R = 6372.8 #Radius of the earth (km)
#spherical law of cosines:
#acos(sin(lat)*sin(lat) + cos(lat)*cos(lat)*cos(delta lon))
delta_rad = acos(sin(pointY)*sin(vecY) +
cos(pointY)*cos(vecY)*cos(delta_lon))
delta_km = R*delta_rad
return(delta_km)
}
vecX and vecY are very large, about 500k elements or more. I want to know
the most efficient way to write this function. I don't even need to do
lapply or an apply function for this because I assume that cos(vector) and
sign(vector) will handle all of the mul...