Question

我在数据框（controids）上具有一组位置的经度和纬度：

library(tidyverse)

centroids <- 
  tribble(
    ~city, ~long, ~lat, 
    "A", -89.92702, 44.19367, 
    "B", -89.92525, 44.19654,
    "C", -89.92365, 44.19756, 
    "D", -89.91949, 44.19848, 
    "E", -89.91359, 44.19818)

我有第二个数据框（towns），其中包含第二组位置的经度和纬度。

towns <- 
  tribble(
    ~town, ~long, ~lat,
    "greentown", -89.92225, 44.19727,
    "bluetown", -89.92997, 44.19899,
    "redtown", -89.91500, 44.19600)

我想在centroids中添加三列，以给出每个城市与towns中三个城镇中每个城镇之间的直线距离（以公里为单位）。因此，最终数据帧将如下所示（距离不正确，仅用于说明）：

output <- 
  tribble(
    ~city, ~long, ~lat, ~greentown_dist, ~bluetown_dist, ~redtown_dist,
    "A", -89.92702, 44.19367, 5.3, 2.0, 1.2,
    "B", -89.92525, 44.19654, 4.4, 2.3, 9.9,
    "C", -89.92365, 44.19756, 3.7, 5.4, 3.3,
    "D", -89.91949, 44.19848, 2.6, 3.9, 6.7,
    "E", -89.91359, 44.19818, 10.2, 2.2, 3.1)

我必须在许多城镇中执行此操作，因此我试图编写一些易于推广的代码。这是我到目前为止所拥有的。

library(sf)

towns <- towns %>% st_as_sf(., coords=c('long', 'lat')) %>% st_geometry()

output <- 
  centroids %>% 
  st_as_sf(., coords=c('long', 'lat')) %>% 
  mutate(greentown_dist = st_distance(geometry, st_point(c( unlist(towns[1]) ))), 
         bluetown_dist = st_distance(geometry, st_point(c( unlist(towns[2]) ))), 
         redtown_dist = st_distance(geometry, st_point(c( unlist(towns[3]) ))))

我想知道是否有一种方法可以使用mutate_at和/或purrr map函数-一种自动填写TOWN_dist列名并输入正确行的函数来自town数据框。

Answer 1

我们可以使用map遍历“城镇”

centroids[paste0(c("green", "blue", "red"), "town_dist")] <- map(towns,
       ~ centroids %>% 
            st_as_sf(., coords = c('long', 'lat')) %>%
            transmute(dist = st_distance(geometry, st_point(c( unlist(.x))))))

在R中使用`mutate_at`或`map`函数来计算多个位置之间的距离

1 个答案: