如何在r中计算多边形文件的质心

Question

我有这个数据集：https://public.opendatasoft.com/explore/dataset/georef-netherlands-postcode-pc4/export/?location=6，52.1564,5.29337&basemap=jawg.light

我需要将它上传到R，并根据经度和纬度提取多边形的质心，这样我就可以用它来计算两个质心之间的距离。

到目前为止，我已经这样做了：

PC4shape <- read_sf(dsn = "georef-netherlands-postcode-pc4", layer = "georef-netherlands-postcode-pc4")
PC4shape$centroids <- st_transform(PC4shape, 28992) %>% 
st_centroid() %>% 
st_transform(., '+proj=longlat +ellps=GRS80 +no_defs') %>%
st_geometry()

以下函数用于使用R 计算两点之间的地理空间距离(纬度、经度(

然而，我确信我的预测和EPSG是错误的。我只是不知道如何找到合适的。非常感谢您的帮助。

Answer 1

不清楚要测量哪些质心，所以下面有几个不同的方法来寻找部分或全部距离。

下面的代码找到每行的质心，显示前两行质心之间的距离，然后是前10行的小距离矩阵。

crs是最初的wgs 84，距离以米为单位。我认为没有必要更换crs。

library(tidyverse)
library(sf)

x <- read_sf('shapefile_dir/') # Replace with local directory name
x <- x %>% mutate(centroids = st_centroid(st_geometry(.)))
#Distance between Goeree-Overflakkee (row 1) and Dordrecht (row 2):
st_distance(x$centroids[1], x$centroids[2])
#> Units: [m]
#>          [,1]
#> [1,] 53317.83
#distance matrix of first 10 rows:
x[1:10,] %>% 
st_set_geometry('centroids') %>%  # Since there are 2 geometry cols, this sets the active one to 'centroids'
st_distance()
#> Units: [m]
#>           [,1]      [,2]      [,3]      [,4]      [,5]      [,6]      [,7]
#>  [1,]     0.00 53317.826 49330.003 85844.745 76152.903 69198.288 89437.405
#>  [2,] 53317.83     0.000  7355.978 38618.416 37934.810 31387.648 45356.081
#>  [3,] 49330.00  7355.978     0.000 38510.970 34633.274 27580.688 44165.444
#>  [4,] 85844.75 38618.416 38510.970     0.000 16873.684 19856.326  8741.436
#>  [5,] 76152.90 37934.810 34633.274 16873.684     0.000  7298.181 14836.265
#>  [6,] 69198.29 31387.648 27580.688 19856.326  7298.181     0.000 20611.458
#>  [7,] 89437.40 45356.081 44165.444  8741.436 14836.265 20611.458     0.000
#>  [8,] 84873.91 42274.715 40485.556  9634.087  9915.349 15823.963  4928.774
#>  [9,] 88788.51 45795.090 44243.643 10476.055 13443.233 19690.611  2255.828
#> [10,] 94857.25 50872.407 49779.022 13205.312 19479.782 25802.514  5617.354
#>            [,8]      [,9]     [,10]
#>  [1,] 84873.911 88788.511 94857.246
#>  [2,] 42274.715 45795.090 50872.407
#>  [3,] 40485.556 44243.643 49779.022
#>  [4,]  9634.087 10476.055 13205.312
#>  [5,]  9915.349 13443.233 19479.782
#>  [6,] 15823.963 19690.611 25802.514
#>  [7,]  4928.774  2255.828  5617.354
#>  [8,]     0.000  3922.534  9994.837
#>  [9,]  3922.534     0.000  6115.383
#> [10,]  9994.837  6115.383     0.000
# A distance matrix of all pairs of points can be found by not
#  subsetting the data:
#  x %>% st_set_geometry('centroids') %>% st_distance()

^{由reprex包(v0.3.0(于2022-03-10创建}