将 SpatVector 对象转换为数据框以在 ggplot2 中使用

Question

我想将SpatVector对象转换为数据框以在 ggplot2 中使用。

pkgs <- c("geodata", "raster", "ggplot2", "tidy")
lapply(pkgs, require, character.only = TRUE)

boundary_GB <- geodata::gadm(country = "GB", path = tempdir(), resolution = 2, level = 1)

我目前的方法需要很长时间：

boundary_GB_df <- broom::tidy(methods::as(boundary_GB, "Spatial"))

剧情：

ggplot(data = boundary_GB_df, mapping = aes(x = long, y = lat, group = group)) +
  geom_polygon(fill = NA, colour = "black")

我对 SpatVector 对象没有经验，有更快的方法吗？

我知道 tidyterra 包（即 tidyterra::geom_spatvector()）。

谢谢

Answer 1

sf对象也是data.frame，您可以使用 ggplot2 ( ) 提供的特定几何图形geom_sf()。R 中空间向量类之间的转换非常简单：

# From SpatVector to sf
sf::st_as_sf(x_spatvector)

# From sf to SpatVector
terra::vect(x_sf)

# To sp, although for most uses is recommended to stick to sf
as(x_sf, "Spatial")

因此，如果 ypu 只需要绘制空间对象，为什么不使用ggplot2::geom_sf()/tidyterra::geom_spatvector()？将对象转换为数据框以进行绘图似乎只是来回，除非您有充分的理由这样做。

参见代表：

library(geodata)
#> Loading required package: terra
#> terra 1.6.17
library(ggplot2)

boundary_GB <- geodata::gadm(country = "GB", path = tempdir(), resolution = 2, level = 1)

class(boundary_GB)
#> [1] "SpatVector"
#> attr(,"package")
#> [1] "terra"

library(sf)
#> Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 6.3.1; sf_use_s2() is TRUE

boundary_GB_sf <- st_as_sf(boundary_GB)

class(boundary_GB_sf)
#> [1] "sf"         "data.frame"
# Is already a data.frame

# sf with geom_sf

ggplot(boundary_GB_sf) +
  geom_sf(fill = NA, colour = "black")

# Spatvector with tidyterra
library(tidyterra)
#> Loading required package: dplyr
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:terra':
#> 
#>     intersect, union
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
#> Loading required package: tibble
#> Loading required package: tidyr
#> 
#> Attaching package: 'tidyr'
#> The following object is masked from 'package:terra':
#> 
#>     extract

ggplot() +
  geom_spatvector(data = boundary_GB, fill = NA, colour = "black")

^{创建于 2022-10-05，使用reprex v2.0.2}