r - 使用 `st_intersection(x)` 后如何获取所有相交多边形的属性？

Question

我想创建一个数据集，其中包含不相交的多边形及其属性，以及两个/所有多边形相交时的属性。

为了演示问题，我创建了一些虚构的数据

set.seed(131)
library(sf)

#create example data
m = rbind(c(0,0), c(1,0), c(1,1), c(0,1), c(0,0))
p = st_polygon(list(m))
n = 20
l = vector("list", n)
for (i in 1:n)
  l[[i]] = p + 10 * runif(2)
s = st_sfc(l)
plot(s, col = sf.colors(categorical = TRUE, alpha = .5))
title("overlapping squares")

#convert to sf object
s <- st_as_sf(s)

#add some random info
s$tree_type <- rep(c("oak", "pine", "fir"), length.out=nrow(s))

看起来像这样

数据如下所示:

Simple feature collection with 20 features and 1 field
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 0.3840939 ymin: 1.132567 xmax: 10.19807 ymax: 10.14945
CRS:           NA
First 10 features:
                                x tree_type
1  POLYGON ((2.06437 1.249422,...       oak
2  POLYGON ((2.932732 3.757797...      pine
3  POLYGON ((8.463468 5.292048...       fir
4  POLYGON ((5.186254 2.378545...       oak
5  POLYGON ((3.263181 9.149452...      pine
6  POLYGON ((4.162483 3.446414...       fir
7  POLYGON ((8.651544 3.160404...       oak
8  POLYGON ((5.231186 2.916041...      pine
9  POLYGON ((0.3840939 6.87075...       fir
10 POLYGON ((7.742229 4.721718...       oak

然后我像这样进行自交

s_intersection <- st_intersection(s)

它创建这样的数据

Simple feature collection with 31 features and 3 fields
Geometry type: GEOMETRY
Dimension:     XY
Bounding box:  xmin: 0.3840939 ymin: 1.132567 xmax: 10.19807 ymax: 10.14945
CRS:           NA
First 10 features:
    tree_type n.overlaps origins                              x
1         oak          1       1 POLYGON ((2.06437 1.249422,...
2        pine          1       2 POLYGON ((3.932732 4.757797...
3         fir          1       3 POLYGON ((8.463468 6.292048...
4         oak          1       4 POLYGON ((6.186254 2.378545...
5        pine          1       5 POLYGON ((3.263181 9.149452...
6         fir          1       6 POLYGON ((4.162483 3.446414...
7         oak          1       7 POLYGON ((9.651544 3.160404...
4.1       oak          2    4, 8 POLYGON ((6.186254 2.916041...
8        pine          1       8 MULTIPOLYGON (((5.826989 3....
9         fir          1       9 POLYGON ((0.3840939 6.87075...

我想要做的是将 origins 列替换为两个多边形的属性。例如，多边形 4.1 将变成oak, pine。或者如果它是两列也可以。我考虑解决这个问题的方法是取消列出origins列中的观察结果，以便每个值都在自己的列中，然后将多边形的属性绑定(bind)到多个中的每个值起源列。但有没有更简单的方法呢？

Answer 1

st_join(s, s, st_intersects)

Simple feature collection with 42 features and 2 fields
Geometry type: POLYGON
Dimension:     XY
Bounding box:  xmin: 0.3840939 ymin: 1.132567 xmax: 10.19807 ymax: 10.14945
CRS:           NA
First 10 features:
    tree_type.x tree_type.y                              x
1           oak         oak POLYGON ((2.06437 1.249422,...
2          pine        pine POLYGON ((2.932732 3.757797...
2.1        pine         oak POLYGON ((2.932732 3.757797...
3           fir         fir POLYGON ((8.463468 5.292048...
3.1         fir         oak POLYGON ((8.463468 5.292048...
4           oak         oak POLYGON ((5.186254 2.378545...
4.1         oak        pine POLYGON ((5.186254 2.378545...
4.2         oak         oak POLYGON ((5.186254 2.378545...
5          pine        pine POLYGON ((3.263181 9.149452...
6           fir         fir POLYGON ((4.162483 3.446414...

您的自相交方向是正确的，但您需要将原始几何体与自身完全相交，因此您可以使用 st_intersects 进行连接来实现这一点。