如何使用dplyr将sf地图对象折叠为多面几何体?
当我使用group_by进行汇总时,默认的最终几何图形似乎是MULTIPOINT sfg类。我想从下面的虚拟数据中绘制3个不同的多边形(每个“区域”值1个),并带有包装传单。
非常感谢任何指导。
library(tidyverse)
library(sf)
library(leaflet)
wannabe_polygons <- st_as_sf(tibble(
area =c(rep("southern suburbs", 8),
rep("northern suburbs", 6),
rep("somerset west", 5)
),
lng = c(18.35, 18.37, 18.34, 18.45,
18.49, 18.43, 18.42, 18.32,
18.49, 18.48, 18.44, 18.7,
18.74, 18.72, 18.82, 18.89,
18.92, 18.87, 18.7
),
lat = c(-34.1, -34.06, -33.99, -33.97,
-34.09, -34.14, -34.19, -34.15,
-33.88, -33.83, -33.7, -33.8,
-33.9, -34.07, -33.9, -33.9,
-34.11, -34.16, -34.05
)
),
coords = c("lng", "lat"))
wannabe_polygons <- wannabe_polygons %>%
group_by(area) %>%
summarise()
# str(wannabe_polygons)
leaflet() %>%
addTiles(group = "OSM") %>%
addPolygons(data = wannabe_polygons)
答案 0 :(得分:0)
不确定为什么要转换为MULTIPOLYGON
,但操作方法如下:
wannabe_polygons %>%
group_by(area) %>%
summarise(geometry = st_combine(geometry)) %>%
st_cast("POLYGON") %>%
summarise(geometry = st_combine(geometry)) -> new_polygons
leaflet() %>%
addProviderTiles(providers$OpenStreetMap) %>%
addPolygons(data = new_polygons)
如果您使用MULTIPOLYGON
或POLYGON
不会对最终的传单地图产生任何影响,因此您可以在st_cast("POLYGON")
之后停下来。