merge_by_intercept.R

merge_by_intercept <- function(buff){
  gt <- rgeos::gIntersects(buff, byid = TRUE, returnDense = FALSE)
  ut <- unique(gt)
  while(sum(duplicated(unlist(unique(ut)))) > 0){
    ut <- unique(sapply(ut, function(x)
      unique(unlist(ut[sapply(ut, function(y) 
        any(x %in% y))]))))
    if(is.matrix(ut)){
      ut <- list(`1` = ut[,1])
      }
    }
  nth <- 1:length(ut)
  buff$n <- 1:nrow(buff)
  buff$nth <- NA
  sapply(seq_along(nth), function(i){
    buff$nth[ut[[i]]] <<- i
  })
  buff <- rgeos::gUnaryUnion(buff, buff$nth)
  return(buff)
}