r - 从数据框中同一行中的两个点创建线串

Question

我想知道是否有一种方法可以根据新几何列中数据框中同一行中给定的两个点创建 linestring。换句话说，两点的经度和纬度在数据框中给出，如下所示：

df <- data.frame(id = c("a", "b"), lon1 = c(1,2), lat1 = c(3,4), lon2 = c(5,6), lat2 = c(7,8))

其中lon1和lat1代表第一个点的坐标，lon2和lat2是第二个点的坐标。所需的数据框将有两行和两列 - id 列和 geometry 列。

我试过 sf::st_linestring 但似乎这个函数只适用于矩阵。

所需的数据帧：

desired_df <- data.frame(id = c("a", "a", "b", "b"), lon = c(1,2,5,6), lat = c(3,4,7,8)) %>% st_as_sf(coords = c("lon", "lat"), dim = "XY") %>% st_set_crs(4236) %>% group_by(id) %>% summarise(geometry = st_union(geometry), do_union = FALSE) %>% st_cast("LINESTRING")

Answer 1

我们可以遍历行，使用 pmap 并将 st_linestring 应用于 matrix 创建的

library(tidyverse)
library(sf)
out <- pmap(df[-1], ~
               c(...) %>%
                matrix(., , ncol=2, byrow = TRUE) %>% 
                st_linestring) %>%
          reduce(st_sfc) %>%
          mutate(df, geometry = .)

out$geometry
#Geometry set for 2 features 
#geometry type:  LINESTRING
#dimension:      XY
#bbox:           xmin: 1 ymin: 3 xmax: 6 ymax: 8
#epsg (SRID):    NA
#proj4string:    NA
#LINESTRING (1 3, 5 7)
#LINESTRING (2 4, 6 8)

Answer 2

更新 - 2021 年 1 月 30 日

我原来的答案的问题是它没有正确设置边界框。

今天我将使用这种方法，使用 sfheaders 和 data.table

library(data.table)
library(sfheaders)

dt <- as.data.table(df)

## To use `sfheaders` the data needs to be in long form

dt1 <- dt[, .(id, lon = lon1, lat = lat1)]
dt2 <- dt[, .(id, lon = lon2, lat = lat2)]

## Add on a 'sequence' variable so we know which one comes first
dt1[, seq := 1L ]
dt2[, seq := 2L ]

## put back together
dt <- rbindlist(list(dt1, dt2), use.names = TRUE)
setorder(dt, id, seq)

sf <- sfheaders::sf_linestring(
  obj = dt
  , x = "lon"
  , y = "lat"
  , linestring_id = "id"
)

sf

# Simple feature collection with 2 features and 1 field
# geometry type:  LINESTRING
# dimension:      XY
# bbox:           xmin: 1 ymin: 3 xmax: 6 ymax: 8
# CRS:            NA
#   id              geometry
# 1  a LINESTRING (1 3, 5 7)
# 2  b LINESTRING (2 4, 6 8)

原答案

使用 data.table

的替代方法

需要(data.table)

dt <- as.data.table(df)

sf <- dt[
    , {
        geometry <- sf::st_linestring(x = matrix(c(lon1, lon2, lat1, lat2), nrow = 2, ncol = 2))
        geometry <- sf::st_sfc(geometry)
        geometry <- sf::st_sf(geometry = geometry)
    }
    , by = id
]

sf::st_as_sf(sf)
# Simple feature collection with 2 features and 1 field
# geometry type:  LINESTRING
# dimension:      XY
# bbox:           xmin: 1 ymin: 3 xmax: 5 ymax: 7
# epsg (SRID):    NA
# proj4string:    NA
# id              geometry
# 1  a LINESTRING (1 3, 5 7)
# 2  b LINESTRING (2 4, 6 8)

Answer 3

此解决方案也使用 purrr 的 pmap，以所需格式获取结果

library(tidyverse)
library(sf) 

df <- data.frame(id = c("a", "b"), lon1 = c(1,2), lat1 = c(3,4), lon2 = c(5,6), lat2 = c(7,8))  

make_line <- function(lon1, lat1, lon2, lat2) {
    st_linestring(matrix(c(lon1, lon2, lat1, lat2), 2, 2))
}

df %>%
    select(-id) %>% 
    pmap(make_line) %>% 
    st_as_sfc(crs = 4326) %>% 
    {tibble(id = df$id, geometry = .)} %>% 
    st_sf()

结果：

Simple feature collection with 2 features and 1 field
geometry type:  LINESTRING
dimension:      XY
bbox:           xmin: 1 ymin: 3 xmax: 6 ymax: 8
epsg (SRID):    4326
proj4string:    +proj=longlat +datum=WGS84 +no_defs
# A tibble: 2 x 2
  id            geometry
  <fct> <LINESTRING [°]>
1 a           (1 3, 5 7)
2 b           (2 4, 6 8)

Answer 4

df = data.frame(id = c("a", "b"), lon1 = c(1,2), lat1 = c(3,4), lon2 = c(5,6), lat2 = c(7,8))  
df

##   id lon1 lat1 lon2 lat2
## 1  a    1    3    5    7
## 2  b    2    4    6    8

这是另一种方式，通过 WKT：

library(sf)
df$geom = sprintf("LINESTRING(%s %s, %s %s)", df$lon1, df$lat1, df$lon2, df$lat2)
df = st_as_sf(df, wkt = "geom")
df

## Simple feature collection with 2 features and 5 fields
## geometry type:  LINESTRING
## dimension:      XY
## bbox:           xmin: 1 ymin: 3 xmax: 6 ymax: 8
## CRS:            NA
##   id lon1 lat1 lon2 lat2                  geom
## 1  a    1    3    5    7 LINESTRING (1 3, 5 7)
## 2  b    2    4    6    8 LINESTRING (2 4, 6 8)

r - 从数据框中同一行中的两个点创建线串

r - Create linestring from two points in same row in dataframe

r

geometry

line

sf

更新 - 2021 年 1 月 30 日

原答案