R/near_eachother.R

In ejanalysis/proxistat: Create a Proximity Score in Each Census Unit, Based on Distances to Specified Points (as in EPA's EJScreen tool, for example)

#' which points are near any of the others in list?
#'
#' @param lon longitude
#' @param lat latitude 
#' @param distance distance between points in miles to check 
#' @param or_tied if TRUE, checks if less than or equal to distance, otherwise if less than
#' @export
#'
near_eachother <- function(lon, lat, distance, or_tied=FALSE) {
  # returns logical vector the length of lon or lat, telling if the point is within distance of any other point in list
# for example,  which sites have residents that might also be near others sites?
df <- data.frame(lon=lon, lat=lat)
  distance_pairs <- proxistat::get.distances.all(df, df)
distance_pairs <- distance_pairs[distance_pairs$fromrow != distance_pairs$torow, ] # remove distance from point to itself
# circles overlap if 2 facilities are twice the radius apart but we just want to check distance here
is_near_any <- (distance_pairs$d < distance) 
original_rownums_near_any <- 1:NROW(lon) %in% distance_pairs$fromrow[is_near_any] 
return(original_rownums_near_any)
# 
# blah <- read.csv('./inst/testpoints_1000.csv')
# nnn <- near_eachother(blah$lon, blah$lat, 10)
# plot(blah$lon, blah$lat, main='red points are the ones near some other point')
# points(blah$lon[nnn],blah$lat[nnn], col='red')
# 
# plot(blah$lon, blah$lat,  main='red points are the ones near some other point')
# points(blah$lon[nnn],blah$lat[nnn], col='red')

}