如何连接两个线串？
可以在线路周围放置一个非常细的缓冲区，然后像这样连接它们:
one_line <- lines %>%
st_buffer(0.05) %>%
st_intersection() %>%
st_union() %>%
st_cast('LINESTRING')
这有两个问题:
a) 下面是我的数据的一个非常小的子集，其中包含一个这样的断开的线段 - 如果我在一小部分上使用上述方法，它会形成一个完整的多边形，当转换为线串时只会形成一个非常窄的环
b) 如果我使用整个数据集，它可以工作，但会在我的原始行周围缓冲区的近似距离处创建行。见下图:
蓝色和红色是边缘线，黑色是原始线。
我想简单地将它们取平均，但是当我将这 2 条线转换为坐标 (st_coordinates()) 时，生成的表格具有不同的长度并且没有按顺序排列。
我环顾四周，但没有真正找到任何有用的答案。
这是几何数据的输入:
lines <- structure(list(structure(list(structure(c(2880, 2880.92, 2881.72,
2882.47, 2883.17, 2883.84, 2884.5, 2894.05, 2894.69, 2895.29393034826,
340255.362641509, 340257.22, 340259.03, 340260.85, 340262.69,
340264.55, 340266.4, 340293.7, 340295.61, 340297.500995024), .Dim = c(10L,
2L)), structure(c(2907.22402724177, 2914.21353757771, 340330.886392736,
340350.2), .Dim = c(2L, 2L))), class = c("XY", "MULTILINESTRING",
"sfg")), structure(c(2895.3, 2896.82, 2897.26, 2897.72, 2907.2,
340297.52, 340302.26, 340303.58, 340304.89, 340330.82), .Dim = c(5L,
2L), class = c("XY", "LINESTRING", "sfg"))), n_empty = 0L, crs = structure(list(
input = "EPSG:31256", wkt = "PROJCRS[\"MGI / Austria GK East\",\n BASEGEOGCRS[\"MGI\",\n DATUM[\"Militar-Geographische Institut\",\n ELLIPSOID[\"Bessel 1841\",6377397.155,299.1528128,\n LENGTHUNIT[\"metre\",1]]],\n PRIMEM[\"Greenwich\",0,\n ANGLEUNIT[\"degree\",0.0174532925199433]],\n ID[\"EPSG\",4312]],\n CONVERSION[\"Austria Gauss-Kruger East\",\n METHOD[\"Transverse Mercator\",\n ID[\"EPSG\",9807]],\n PARAMETER[\"Latitude of natural origin\",0,\n ANGLEUNIT[\"degree\",0.0174532925199433],\n ID[\"EPSG\",8801]],\n PARAMETER[\"Longitude of natural origin\",16.3333333333333,\n ANGLEUNIT[\"degree\",0.0174532925199433],\n ID[\"EPSG\",8802]],\n PARAMETER[\"Scale factor at natural origin\",1,\n SCALEUNIT[\"unity\",1],\n ID[\"EPSG\",8805]],\n PARAMETER[\"False easting\",0,\n LENGTHUNIT[\"metre\",1],\n ID[\"EPSG\",8806]],\n PARAMETER[\"False northing\",-5000000,\n LENGTHUNIT[\"metre\",1],\n ID[\"EPSG\",8807]]],\n CS[Cartesian,2],\n AXIS[\"northing (X)\",north,\n ORDER[1],\n LENGTHUNIT[\"metre\",1]],\n AXIS[\"easting (Y)\",east,\n ORDER[2],\n LENGTHUNIT[\"metre\",1]],\n USAGE[\n SCOPE[\"Engineering survey, topographic mapping.\"],\n AREA[\"Austria east of 14°50'E of Greenwich (32°30'E of Ferro).\"],\n BBOX[46.56,14.83,49.02,17.17]],\n ID[\"EPSG\",31256]]"), class = "crs"), idx = structure(c(1,
2, 1, 1), .Dim = c(2L, 2L)), class = c("sfc_GEOMETRY", "sfc"), precision = 0, bbox = structure(c(xmin = 2880,
ymin = 340255.362641509, xmax = 2914.21353757771, ymax = 340350.2
), class = "bbox"), classes = c("MULTILINESTRING", "LINESTRING"
))
最佳答案
对于上面的示例，您可以转换为 MULTIPOINT，然后联合，然后转换为 LINESTRING。
``` r
library(tidyverse) #overkill, but easier
library(sf)
library(patchwork) #to plot side-by-side
# load data from above
# lines <-
single_line <- lines %>%
st_as_sf() %>%
st_cast('MULTIPOINT') %>%
st_union() %>%
st_cast('LINESTRING')
head(single_line)
#> Geometry set for 1 feature
#> Geometry type: LINESTRING
#> Dimension: XY
#> Bounding box: xmin: 2880 ymin: 340255.4 xmax: 2914.214 ymax: 340350.2
#> Projected CRS: MGI / Austria GK East
#> LINESTRING (2880 340255.4, 2880.92 340257.2, 28...
p1 <- ggplot() +
geom_sf(data = st_as_sf(lines), col = c('red', 'blue')) + ggtitle('lines')
p2 <- ggplot() + geom_sf(data = single_line, col = 'black') + ggtitle('lines cast & unioned')
p3 <- p1 + p2
p3
由 reprex package 创建于 2022-03-08 (v0.3.0)
关于r - 连接线串，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/71394190/