从具有多个坐标的数据框创建sf对象|R sf

Question

我想从一个数据框中创建一个sf对象，该数据框在每行的不同列下包含多个坐标。在下面的repex中，每个ID都包含纬度和经度的开始和结束坐标。

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dfr <- structure(list(ID = c("1001A", "1002A", "1003A", "1004A", "1005A", 
"1006A", "1007A", "1008A", "1009A", "1010A"), StartLat = c(33.53418, 
33.60399, 33.40693, 33.64672, 33.57127, 33.42848, 33.54936, 33.49554, 
33.5056, 33.61696), StartLong = c(-112.09114, -111.92731, -112.02982, 
-111.92548, -112.04899, -112.0998, -112.09123, -111.9687, -112.05629, 
-111.98657), EndLat = c(33.53488, 33.60401, 33.40687, 33.64776, 
33.57125, 33.42853, 33.54893, 33.49647, 33.5056, 33.61654), EndLong = c(-112.09114, 
-111.93097, -112.03429, -111.93031, -112.04807, -112.09929, -112.09122, 
-111.97105, -112.0541, -111.98657)), row.names = c(3028L, 8618L, 
6322L, 1171L, 691L, 6590L, 2008L, 4552L, 2894L, 1909L), class = "data.frame")

我尝试使用sf包的st_as_sf函数，但产生了一个错误：

dfr_sf <- st_as_sf(dfr, coords = c(c("StartLong", "EndLong"), c("StartLat", "EndLat")),
                   crs = "+proj=longlat +datum=WGS84")

Error in points_rcpp(as.matrix(cc), dim) : 
  dim(pts)[2] == nchar(gdim) is not TRUE

每行中的起点和终点坐标定义了一个路段。所有坐标都应位于最终sf对象中的几何图形列下，以便这些坐标可以绘制为多段线。

Answer 1

请查看dfr_line是否是您想要的。我认为我们首先需要创建一个point sf对象，然后将其转换为linestring。

library(tidyverse)
library(sf)

dfr2 <- dfr %>%
  pivot_longer(-ID, names_to = c("Type", ".value"), names_pattern = "(^[A-Z][a-z]+)([A-Z][a-z]+$)")

dfr_point <- dfr2 %>%
  st_as_sf(coords = c("Long", "Lat"), crs = "+proj=longlat +datum=WGS84")

dfr_line <- dfr_point %>%
  group_by(ID) %>%
  summarize() %>%
  st_cast("LINESTRING")