使用SF包按多点分割线 [英] Split line by multiple points using sf package
本文介绍了使用SF包按多点分割线的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在尝试通过沿线对点将大线形分割.根据先前主要由@mbcaradima提出的问题，此处，此处，此处和
I am trying to split a large line shape by pairs of points along the line. Based on previous questions asked mainly by @mbcaradima here, here, here and here, I have put together some code which works for single points, but does not for multiple points.
请参见下面的可复制示例:
See reproducible example below:
# libraries
library(tidyverse)
library(sf)
library(rgdal)
library(sp)
river <- structure(list(FWK_Code = structure(1L, .Label = "1_F461", class = "factor"),
FWK_Name = structure(1L, .Label = "Glonn von Odelzhausen bis Mündung in die Amper", class = "factor"),
Achse_SWK = structure(NA_integer_, .Label = character(0), class = "factor"),
GEWKZ_11 = structure(1L, .Label = "1648", class = "factor"),
NAM11_SEG = structure(1L, .Label = "Glonn", class = "factor"),
GWO11_SEG = structure(1L, .Label = "1330", class = "factor"),
FKT11_SEG = structure(1L, .Label = "2403", class = "factor"),
ZUST_WWA = structure(1L, .Label = "M", class = "factor"),
ZUST_REG = structure(1L, .Label = "OB", class = "factor"),
FF_LAND = structure(1L, .Label = "DEBY", class = "factor"),
GEW_TYP_K = structure(1L, .Label = "F2.2", class = "factor"),
GEW_TYP_L = structure(1L, .Label = "Kleine Flüsse des Alpenvorlandes", class = "factor"),
HMWB = structure(1L, .Label = "HMWB", class = "factor"),
length_m = 27210, code_vis = structure(1L, .Label = "1_F461", class = "factor"),
geometry = structure(list(structure(c(4454482.82717063, 4454477.69,
4454464.67, 4454447.61, 4454437.73, 4454426.51, 4454409.9,
4454391.94, 4454373.98, 4454359.62, 4454344.8, 4454335.82,
4454317.21, 4454313.45, 4454312.77, 4454309.34, 4454300.59,
4454291.38, 4454284.64, 4454268.93, 4454253.67, 4454234.36,
4454211.47, 4454186.33, 4454158.04, 4454140.98, 4454133.83,
4454125.77, 4454120.53, 4454117.07, 4454097.87, 4454073.83,
4454011.25, 4453877.38, 4453783.85, 4453742.74, 4453742.32,
4453727.02, 4453716.29, 4453710.08, 4453698.84, 4453688.08,
4453682.1, 4453664.37, 4453653.96, 4453641.58, 4453618.07,
4453588.82, 4453561.8, 4453548.29, 4453537.32, 4453529.3,
4453523.71, 4453522.55, 4453517.06, 4453514.53, 4453514.95,
4453523.81, 4453525.5, 4453522.97, 4453510.31, 4453495.53,
4453463.67, 4453452.21, 4453432.45, 4453423.25, 4453395.29,
4453350.73, 4453259.43, 4453181.41, 4453163.58, 4453158.68,
4453154.58, 4453146.63, 4453134.59, 4453098.66, 4453000.7,
4452909.68, 4452627.91, 4452620.51, 4452562.96, 4452508.19,
4452448.4, 4452400.29, 4452376.72, 4452311.09, 4452225.2,
4452203.98, 4452176.98, 4452166.66, 4452135.14, 4452101.77,
4452052.37, 4452014.28, 4451988.32, 4451899.24, 4451893.85,
4451871.58, 4451817.72, 4451785.2, 4451761.21, 4451731.24,
4451712.01, 4451693.25, 4451682.14, 4451657.13, 4451636.02,
4451630.51, 4451622.89, 4451615.39, 4451591.93, 4451581.61,
4451560.51, 4451537.06, 4451523.92, 4451511.73, 4451483.78,
4451476.25, 4451471.86, 4451469.3, 4451438.56, 4451384.62,
4451284.5, 4451259.71, 4451221.42, 4451119.19, 4451110.21,
4451107.87, 4451099.18, 4451091.28, 4451046.03, 4450945.32,
4450884.24, 4450846.94, 4450819.81, 4450790.1, 4450758.62,
4450714.54, 4450696.54, 4450669.05, 4450656.15, 4450619.21,
4450587.43, 4450583.75, 4450567.55, 4450507.21, 4450483.95,
4450465.2, 4450375.63, 4450354.81, 4450328, 4450252.04, 4450237.08,
4450220.65, 4450187.34, 4450152.66, 4450131.38, 4450124.66,
4450110.43, 4450085.02, 4450056.18, 4450033.86, 4450018.41,
4449976.87, 4449966.73, 4449964.81, 4449954.93, 4449938.61,
4449917.72, 4449902.2, 4449887.72, 4449884.86, 4449859, 4449853.42,
4449849, 4449844.8, 4449803.42, 4449777.71, 4449752.73, 4449744.70318071,
5358599.95603184, 5358596.63, 5358590.34, 5358582.71, 5358576.42,
5358568.79, 5358556.22, 5358541.86, 5358527.04, 5358514.47,
5358500.11, 5358493.82, 5358477.42, 5358473.28, 5358472.52,
5358468.68, 5358456.59, 5358443.54, 5358432.76, 5358410.32,
5358389.67, 5358362.73, 5358328.61, 5358290.45, 5358242.86,
5358215.93, 5358210, 5358204.52, 5358201.19, 5358198.95,
5358187.14, 5358181.75, 5358176.36, 5358173.05, 5358175.29,
5358176.19, 5358176.2, 5358172.41, 5358157.12, 5358147.5,
5358123.63, 5358104, 5358093.08, 5358067.75, 5358055.79,
5358041.58, 5358016, 5357984.17, 5357955.89, 5357933.94,
5357912.84, 5357896.38, 5357876.81, 5357872.74, 5357846.99,
5357828.42, 5357811.11, 5357733.87, 5357711.07, 5357689.55,
5357645.65, 5357603.02, 5357523.83, 5357493.98, 5357445.35,
5357424.83, 5357379.53, 5357334.4, 5357245.54, 5357170.31,
5357153.66, 5357149.82, 5357146.6, 5357140.36, 5357130.91,
5357110.43, 5357055.29, 5357002.09, 5356939.82, 5356937.7,
5356920.74, 5356906.82, 5356890.51, 5356880.48, 5356875.56,
5356856.4, 5356828.51, 5356822.82, 5356812.72, 5356808.62,
5356788.72, 5356764.09, 5356726.68, 5356706.5, 5356696.34,
5356684.31, 5356683.6, 5356679.74, 5356656.68, 5356636.56,
5356613.5, 5356583.86, 5356560.41, 5356531.79, 5356511.3,
5356451.12, 5356398.12, 5356387.4, 5356381.23, 5356374.67,
5356363.88, 5356362, 5356357.31, 5356355.43, 5356355.43,
5356357.31, 5356362.31, 5356363.6, 5356364.35, 5356364.6,
5356367.63, 5356373.26, 5356382.3, 5356382.62, 5356379.07,
5356353.88, 5356351.95, 5356351.44, 5356348.99, 5356347.05,
5356335.95, 5356307.71, 5356291.47, 5356283.7, 5356278.35,
5356278.2, 5356289.69, 5356311.72, 5356321.69, 5356330.54,
5356332.74, 5356335.88, 5356329.43, 5356328.02, 5356321.84,
5356294.15, 5356285.09, 5356277.79, 5356250.55, 5356243.77,
5356235.05, 5356200.51, 5356193.71, 5356184.67, 5356163.04,
5356144.16, 5356135.23, 5356134.24, 5356132.14, 5356131.8,
5356136.6, 5356145.19, 5356151.37, 5356173.49, 5356177.49,
5356178.04, 5356178.04, 5356176.53, 5356173.65, 5356168.12,
5356161.8, 5356159.97, 5356138.51, 5356131.75, 5356126.26,
5356121.43, 5356074.91, 5356049.16, 5356016.55, 5356007.68509448
), .Dim = c(180L, 2L), class = c("XY", "LINESTRING", "sfg"
))), class = c("sfc_LINESTRING", "sfc"), precision = 0, bbox = structure(c(xmin = 4449744.70318071,
ymin = 5356007.68509448, xmax = 4454482.82717063, ymax = 5358599.95603184
), class = "bbox"), crs = structure(list(epsg = NA_integer_,
proj4string = "+proj=tmerc +lat_0=0 +lon_0=12 +k=1 +x_0=4500000 +y_0=0 +ellps=bessel +towgs84=598.1,73.7,418.2,0.202,0.045,-2.455,6.7 +units=m +no_defs"), class = "crs"), n_empty = 0L)), row.names = 0L, class = c("sf",
"data.frame"), sf_column = "geometry", agr = structure(c(FWK_Code = NA_integer_,
FWK_Name = NA_integer_, Achse_SWK = NA_integer_, GEWKZ_11 = NA_integer_,
NAM11_SEG = NA_integer_, GWO11_SEG = NA_integer_, FKT11_SEG = NA_integer_,
ZUST_WWA = NA_integer_, ZUST_REG = NA_integer_, FF_LAND = NA_integer_,
GEW_TYP_K = NA_integer_, GEW_TYP_L = NA_integer_, HMWB = NA_integer_,
length_m = NA_integer_, code_vis = NA_integer_), class = "factor", .Label = c("constant",
"aggregate", "identity")))
sites <- st_line_sample(river, density = 1/1500) %>%
st_jitter(500) %>%
st_sf() %>%
st_cast('POINT') %>%
mutate(group = c(1,1,2,2)) %>%
mutate(type = rep(c("start","stop"),2))
mapview(sites) + river
对齐到行&点分割-单点
仅使用一个站点，以下代码即可工作.由于飞溅点未与线完全相交，因此我添加了一个小缓冲区.这很难说是优雅，但可以满足我的情况.
Snap to line & split at points - single point
Using only a single site, the following code works. As the spapped points do not exactly intersect the line, I have added a small buffer. This is hardly elegant, but will do for my situation.
nrst = st_nearest_points(sites, river)
on_line = st_cast(nrst, "POINT")[2]
buf <- st_buffer(on_line,0.1)
parts = st_collection_extract(lwgeom::st_split(river$geometry, buf),"LINESTRING")
mapview(parts[1],color="red",lwd=5) + mapview(parts[2],color="green",lwd=5) + mapview(parts[3],lwd=5)
对齐到行&点分割-多点
使用多个站点会产生Error in st_split.sfc(river$geometry, buf_all) :
length(y) == 1 is not TRUE
Snap to line & split at points - multiple points
Using multiple sites produces Error in st_split.sfc(river$geometry, buf_all) :
length(y) == 1 is not TRUE
on_line_all = st_cast(nrst, "POINT")
buf_all <- st_buffer(on_line_all,0.1)
parts_all = st_collection_extract(lwgeom::st_split(river$geometry, buf_all),"LINESTRING")
不幸的是，在这种情况下，我不确定"y"是什么.同样，如果可以将成对的起点和终点之间的所有线段自动保存到一个单独的对象中，而不必例如手动选择它们，则将是理想的. QGIS.
Unfortunately, in this case, I'm not sure what "y" is. Also, it would be ideal, if all line segments between pairs of start and stop points could be saved to a separate object automatically, rather than having to select them by hand in e.g. QGIS.
任何建议将不胜感激！
推荐答案
结果证明lwgeom::st_split的文档中存在错误.它指出y是
Turns out there is an error in the documentation for lwgeom::st_split. It states that y is the
用(刀片)分割的对象；如果y包含多个要素几何，则这些几何为st_combined
object split with (blade); if y contains more than one feature geometry, the geometries are st_combined
但是，在提供多功能sfc时(如您的情况)，它们不会被st_combine d.
However, they are not st_combined when supplying a multi-feature sfc (as in your case).
要使您的st_split正常工作，您需要预先将它们组合在一起:
To get your st_split to work, you'd need to combine them beforehand:
on_line_all = st_cast(nrst, "POINT")
buf_all <- st_combine(st_buffer(on_line_all,0.1))
parts_all = st_collection_extract(lwgeom::st_split(river$geometry, buf_all),"LINESTRING")
parts_all = st_as_sf(
data.frame(
id = 1:length(parts_all),
geometry = parts_all
)
)
mapview(parts_all, burst = "id")
这篇关于使用SF包按多点分割线的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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