How to find point related to set of coordinates?

Question

I have a set of about 5000 geographical (WGS84) coordinates. All of them are inside 40km square.

Is there any algorithm / R function to find point, inside square and not

Answer 1

Here's an example that uses several functions (distanceFromPoints(), maxValue(), Which(), and xyFromCell()) from the raster package to perform the key calculations:

# Load required libraries
library(sp)
library(rgdal)
library(raster)

# Create a SpatialPoints object with 10 points randomly sampled from
# the area lying between longitudes 0 and 1 and latitudes 0 and 1
bbox <- matrix(c(0,0,1,1), ncol=2, dimnames = list(NULL, c("min", "max")))
PRJ4 <- CRS("+proj=longlat +datum=WGS84 +ellps=WGS84")
S <- Spatial(bbox = bbox, proj4string = PRJ4)
SP <- spsample(S, 10, type="random")

# Create a raster object covering the same area
R <- raster(extent(bbox), nrow=100, ncol=100, crs=PRJ4)

# Find the coordinates of the cell that is farthest from all of the points
D <- distanceFromPoints(object = R, xy = SP) 
IDmaxD <- Which(D == maxValue(D), cells=TRUE)
(XY <- xyFromCell(D, IDmaxD))
#          x     y
# [1,] 0.005 0.795

# Plot the results
plot(D, main = "Distance map, with most distant cell in red")
points(SP)
points(XY, col="red", pch=16, cex=2)