如何将类从数据框更改为空间多边形？

Question

我在这里如何将数据框转换为空间坐标中找到了相同的内容。 但就我而言，我得到了非常大的数据。

exchange    longitude   latitude
AB  103.3281386 1.594218196
AB  103.3285929 1.593990735
AB  103.3312494 1.591424235
AB  103.3283736 1.594063254
AB  103.3536164 1.622771588
AB  103.3613242 1.627138676
AB  103.3560151 1.619455334
AB  103.3297071 1.593398614
AB  103.3269466 1.596574285
AB  103.3279517 1.593614052
AB  103.3281356 1.593848271
AB  103.3567136 1.620498495
AB  103.3668021 1.63456952
AB  103.359686  1.624821271
AB  103.3308963 1.585290892
AB  103.3319569 1.59104387
AB  103.3307149 1.592006748
AB  103.3283657 1.593675616
AB  103.3314873 1.591186363
AB  103.3319648 1.590585241
AB  103.3321508 1.590422594
AB  103.3318503 1.588685843
AB  103.3324507 1.594547225
AB  103.3442528 1.60909707
AB  103.3292733 1.593461728
AB  103.3288584 1.594312512
AB  103.329041  1.594135083
AB  103.3348961 1.59761749
AB  103.3500524 1.614224612

不可能像他们那样做：

mydf <- structure(list(longitude = c(128.6979, 153.0046, 104.3261, 124.9019, 
126.7328, 153.2439, 142.8673, 152.689), latitude = c(-7.4197, 
-4.7089, -6.7541, 4.7817, 2.1643, -5.65, 23.3882, -5.571)), .Names = c("longitude", 
"latitude"), class = "data.frame", row.names = c(NA, -8L))

那么任何人都可以帮助我将类从 data.frame 更改为空间多边形？

Answer 1

我的数据与其他帖子相同 [...] 所以任何人都可以帮助我将类从 data.frame 更改为空间多边形？

library(sp)
sp <- SpatialPolygons(list(Polygons(list(Polygon(mydf[, -1])), ID=1)))
class(sp)
# [1] "SpatialPolygons"
# attr(,"package")
# [1] "sp"

或者，如果您希望exchange成为多边形标识符：

sp <- lapply(split(mydf[, -1], mydf[, 1]), Polygon)
sp <- SpatialPolygons(lapply(seq_along(sp), function(i) { 
  Polygons(list(sp[[i]]), ID = row.names(mydf[!duplicated(mydf[, 1]), ])[i] ) 
}))
# class(sp)
# [1] "SpatialPolygons"
# attr(,"package")
# [1] "sp"

数据：

mydf <- read.table(header=T, text="
exchange   longitude   latitude
AB  103.3281386 1.594218196
AB  103.3285929 1.593990735
AB  103.3312494 1.591424235
AB  103.3283736 1.594063254
AB  103.3536164 1.622771588
AB  103.3613242 1.627138676
AB  103.3560151 1.619455334
AB  103.3297071 1.593398614
AB  103.3269466 1.596574285
AB  103.3279517 1.593614052
AB  103.3281356 1.593848271
AB  103.3567136 1.620498495
AB  103.3668021 1.63456952
AB  103.359686  1.624821271
AB  103.3308963 1.585290892
AB  103.3319569 1.59104387
AB  103.3307149 1.592006748
AB  103.3283657 1.593675616
AB  103.3314873 1.591186363
AB  103.3319648 1.590585241
AB  103.3321508 1.590422594
AB  103.3318503 1.588685843
AB  103.3324507 1.594547225
AB  103.3442528 1.60909707
AB  103.3292733 1.593461728
AB  103.3288584 1.594312512
AB  103.329041  1.594135083
AB  103.3348961 1.59761749
AB  103.3500524 1.614224612")