我如何找到一个方向，即polygon_sf2的最接近点来自polygon_sf1，分为八个方向之一（北，东北，东，东南，东南，南，西南，西，西，西北，西北）。 ..

Question

这可能会让您入门。 Initialise

Answer 1

-Objects。可以简化此步骤。

 library(sf)
 p1 = st_as_sf(as.data.frame(coords1), coords = c("V1", "V2"), crs = 4269) 
 polygon_sf1 = st_sf(st_sfc(st_polygon(list(coords1)), crs = 4326))
 p2 = st_as_sf(as.data.frame(coords2), coords = c("V1", "V2"), crs = 4269) 
 polygon_sf2 = st_sf(st_sfc(st_polygon(list(coords2)), crs = 4326))
 o = st_nearest_points(polygon_sf1, polygon_sf2)

从这个this this this

答案

借来

 first_last_dir = \(xy) geosphere::bearing(xy[1, 1:2], xy[nrow(xy), 1:2])
 
 orient = \(lines) {
  lines |>
    sf::st_coordinates() |>
    data.frame() |>
    split(~L1) |>
    sapply(first_last_dir)
  }

为心内方向创建参考载体

 cardinal_direction = 
   setNames(seq(0, 360, 45), c('north', 'north-east', 'east',' south-east', 'south',' south-west', 'west', 'north-west'))

苹果

 names(cardinal_direction)[findInterval(orient(o), cardinal_direction)]
#> [1] "north-east"

关于索引的其他选择还有很多其他选择。解释留给您。 plot

 library(ggplot2)
 ggplot() +
   geom_sf(data = polygon_sf2) +
   geom_sf(data = polygon_sf1) +
   geom_sf(data = o)

data

 coords1 = matrix(c(
   -1.6522, 55.571,
   -1.6487, 55.568,
   -1.6522, 55.565,
   -1.6550, 55.568,
   -1.6522, 55.571
 ), ncol = 2, byrow = TRUE)

 coords2 = matrix(c(
   -1.645, 55.575,
   -1.6449, 55.571,
   -1.6472, 55.569,
   -1.649, 55.571,
   -1.645, 55.575
 ), ncol = 2, byrow = TRUE)