如何将 geom_sf 生成的地图放在 ggmap 生成的栅格之上 [英] How to put a geom_sf produced map on top of a ggmap produced raster

问题描述

我尝试了以下代码:

库(ggplot2)图书馆(ggmap)图书馆(SF)nc <- st_read(system.file("shape/nc.shp", package = "sf"))str(nc)类‘sf’和‘data.frame’:100 obs.共 15 个变量:美元面积:数量 0.114 0.061 0.143 0.07 0.153 0.097 0.062 0.091 0.118 0.124 ...$ 周长:num 1.44 1.23 1.63 2.97 2.21 ...$ CNTY_ : 编号 1825 1827 1828 1831 1832 ...$ CNTY_ID : 编号 1825 1827 1828 1831 1832 ...$ NAME :具有 100 个级别Alamance"、Alexander"、..的因子:5 3 86 27 66 46 15 37 93 85 ...$ FIPS :因子 w/100 级别 "37001","37003",..: 5 3 86 27 66 46 15 37 93 85 ...$ FIPSNO : 编号 37009 37005 37171 37053 37131 ...$ CRESS_ID : int 5 3 86 27 66 46 15 37 93 85 ...$ BIR74:编号 1091 487 3188 508 1421 ...$ SID74 : 数量 1 0 5 1 9 7 0 0 4 1 ...$ NWBIR74:编号 10 10 208 123 1066 ...$ BIR79:编号 1364 542 3616 830 1606 ...$ SID79 : 编号 0 3 6 2 3 5 2 2 2 5 ...$ NWBIR79:编号 19 12 260 145 1197 ...$几何:长度为100的sfc_MULTIPOLYGON；第一个列表元素:1 的列表..$ :1 的列表.. ..$ : num [1:27, 1:2] -81.5 -81.5 -81.6 -81.6 -81.7 .....- attr(*, "class")= chr "XY" "MULTIPOLYGON" "sfg"- attr(*, "sf_column")= chr "几何"- attr(*, "agr")= 因子 w/3 个级别 "constant","aggregate",..: NA NA NA NA NA NA NA NA NA .....- attr(*, "names")= chr "AREA" "PERIMETER" "CNTY_" "CNTY_ID" ...地图 <- get_map("北卡罗来纳州", maptype = "satellite", zoom = 6, source = "google")a <- unlist(attr(map,"bb")[1, ])bb <- st_bbox(nc)ggplot() +annotation_raster(map, xmin = a[2], xmax = a[4], ymin = a[1], ymax = a[3]) +xlim(c(bb[1], bb[3])) + ylim(c(bb[2], bb[4])) +geom_sf(data = nc, aes(fill = AREA))

两层没有正确重叠；我尝试使用 coord_sf() 更改投影，但没有成功.

有什么建议吗?谢谢

解决方案

我自己也在努力解决这个问题，并在 (v0.2.0) 于 2018 年 6 月 13 日创建.

I tried the following code:

library(ggplot2)
library(ggmap)
library(sf)
nc <- st_read(system.file("shape/nc.shp", package = "sf"))
str(nc)

 Classes ‘sf’ and 'data.frame':  100 obs. of  15 variables:
 $ AREA     : num  0.114 0.061 0.143 0.07 0.153 0.097 0.062 0.091 0.118 0.124 ...
 $ PERIMETER: num  1.44 1.23 1.63 2.97 2.21 ...
 $ CNTY_    : num  1825 1827 1828 1831 1832 ...
 $ CNTY_ID  : num  1825 1827 1828 1831 1832 ...
 $ NAME     : Factor w/ 100 levels "Alamance","Alexander",..: 5 3 86 27 66 46 15 37 93 85 ...
 $ FIPS     : Factor w/ 100 levels "37001","37003",..: 5 3 86 27 66 46 15 37 93 85 ...
 $ FIPSNO   : num  37009 37005 37171 37053 37131 ...
 $ CRESS_ID : int  5 3 86 27 66 46 15 37 93 85 ...
 $ BIR74    : num  1091 487 3188 508 1421 ...
 $ SID74    : num  1 0 5 1 9 7 0 0 4 1 ...
 $ NWBIR74  : num  10 10 208 123 1066 ...
 $ BIR79    : num  1364 542 3616 830 1606 ...
 $ SID79    : num  0 3 6 2 3 5 2 2 2 5 ...
 $ NWBIR79  : num  19 12 260 145 1197 ...
 $ geometry :sfc_MULTIPOLYGON of length 100; first list element: List of 1
 ..$ :List of 1
 .. ..$ : num [1:27, 1:2] -81.5 -81.5 -81.6 -81.6 -81.7 ...
   ..- attr(*, "class")= chr  "XY" "MULTIPOLYGON" "sfg"
   - attr(*, "sf_column")= chr "geometry"
   - attr(*, "agr")= Factor w/ 3 levels "constant","aggregate",..: NA NA NA NA NA NA NA NA NA NA ...
   ..- attr(*, "names")= chr  "AREA" "PERIMETER" "CNTY_" "CNTY_ID" ...

map <- get_map("north carolina", maptype = "satellite", zoom = 6, source = "google")
a <- unlist(attr(map,"bb")[1, ])
bb <- st_bbox(nc)
ggplot() + 
  annotation_raster(map, xmin = a[2], xmax = a[4], ymin = a[1], ymax = a[3]) + 
  xlim(c(bb[1], bb[3])) + ylim(c(bb[2], bb[4])) + 
  geom_sf(data = nc, aes(fill = AREA))

The two layers do not overlap properly; I tried changing projection with coord_sf() but I did not have success.

any suggestion? thanks

解决方案

I've struggled with this myself, and with the help of this post I've come up with a solution. The bounding box of the ggmap object is in WGS84 (EPSG:4326), but the actual raster is in EPSG:3857. You have to hack the bounding box of the ggmap object to be in the same CRS as the underlying data:

library(ggplot2)
library(ggmap)
library(sf)
#> Linking to GEOS 3.6.2, GDAL 2.3.0, proj.4 5.1.0

nc <- st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)

# Transform nc to EPSG 3857 (Pseudo-Mercator, what Google uses)
nc_3857 <- st_transform(nc, 3857)

map <- get_map("north carolina", maptype = "satellite", zoom = 6, source = "google")

# Define a function to fix the bbox to be in EPSG:3857
ggmap_bbox <- function(map) {
  if (!inherits(map, "ggmap")) stop("map must be a ggmap object")
  # Extract the bounding box (in lat/lon) from the ggmap to a numeric vector, 
  # and set the names to what sf::st_bbox expects:
  map_bbox <- setNames(unlist(attr(map, "bb")), 
                       c("ymin", "xmin", "ymax", "xmax"))

  # Coonvert the bbox to an sf polygon, transform it to 3857, 
  # and convert back to a bbox (convoluted, but it works)
  bbox_3857 <- st_bbox(st_transform(st_as_sfc(st_bbox(map_bbox, crs = 4326)), 3857))

  # Overwrite the bbox of the ggmap object with the transformed coordinates 
  attr(map, "bb")$ll.lat <- bbox_3857["ymin"]
  attr(map, "bb")$ll.lon <- bbox_3857["xmin"]
  attr(map, "bb")$ur.lat <- bbox_3857["ymax"]
  attr(map, "bb")$ur.lon <- bbox_3857["xmax"]
  map
}

# Use the function:
map <- ggmap_bbox(map)

ggmap(map) + 
  coord_sf(crs = st_crs(3857)) + # force the ggplot2 map to be in 3857
  geom_sf(data = nc_3857, aes(fill = AREA), inherit.aes = FALSE)

Created on 2018-06-13 by the reprex package (v0.2.0).

这篇关于如何将 geom_sf 生成的地图放在 ggmap 生成的栅格之上的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！