1suppressPackageStartupMessages(library(sf))
2library(sp)
3suppressPackageStartupMessages(library(units))
4
5x = st_sfc(
6st_point(c(0,0)),
7st_point(c(1,0)),
8st_point(c(2,0)),
9st_point(c(3,0)),
10crs = 4326
11)
12
13y = st_sfc(
14st_point(c(0,10)),
15st_point(c(1,0)),
16st_point(c(2,0)),
17st_point(c(3,0)),
18st_point(c(4,0)),
19crs = 4326
20)
21
22d.sf = st_distance(x, y)
23d.sp = spDists(as(x, "Spatial"), as(y, "Spatial"))
24units(d.sp) = as_units("km")
25round(d.sf - d.sp, 7)
26
27#summary(unclass(d.sf) - d.sp)
28
29st_crs(x) = st_crs(y) = NA
30d.sf = st_distance(x, y)
31d.sp = spDists(as(x, "Spatial"), as(y, "Spatial"))
32round(d.sf - d.sp, 7)
33
34# st_length:
35st_crs(y) = 4326
36(z = st_sfc(st_linestring(rbind(c(0,10), c(1,0), c(2,0), c(3,0), c(4,0))), crs = 4326))
37d = st_distance(y, y)
38round(d, 7)
39st_length(z)
40st_length(z) - sum(d[1,2], d[2,3], d[3,4], d[4,5])
41
42# st_line_sample:
43ls = st_sfc(st_linestring(rbind(c(0,0),c(0,1))),
44	st_linestring(rbind(c(0,0),c(10,0))))
45# set.seed(135)
46st_line_sample(ls, density = 1)
47
48ls = st_sfc(st_linestring(rbind(c(0,0),c(0,1))),
49	st_linestring(rbind(c(0,0),c(.1,0))), crs = 4326)
50
51st_length(ls)
52try(st_line_sample(ls, density = 1/1000))
53x = st_line_sample(st_transform(ls, 3857), density = 1/1000) # one per km
54