library(sfnetworks)
library(sf)
#> Linking to GEOS 3.7.1, GDAL 2.2.2, PROJ 4.9.2
library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union

paths = as_sfnetwork(roxel, directed = FALSE) %>%
  st_transform(3035) %>%
  st_shortest_paths(from = 1, to = c(9,10))

paths
#> # A tibble: 2 x 2
#>   node_paths edge_paths
#>   <list>     <list>    
#> 1 <int [17]> <int [16]>
#> 2 <int [18]> <int [17]>

paths %>%
  slice(1) %>%
  pull(node_paths) %>%
  unlist()
#>  [1]   1 644 579 260 164 208 426 424 533 657 512 506 111 524 292 167   9

library(sfnetworks)
library(sf)
library(dplyr)
library(purrr)

paths = as_sfnetwork(roxel, directed = FALSE) %>%
  st_transform(3035) %>%
  st_shortest_paths(from = 2, to = c(110:120))
#> Warning in (function (graph, from, to = V(graph), mode = c("out", "all", : At
#> structural_properties.c:745 :Couldn't reach some vertices

paths
#> # A tibble: 11 x 2
#>    node_paths edge_paths
#>    <list>     <list>    
#>  1 <int [20]> <int [19]>
#>  2 <int [14]> <int [13]>
#>  3 <int [10]> <int [9]> 
#>  4 <int [9]>  <int [8]> 
#>  5 <int [17]> <int [16]>
#>  6 <int [18]> <int [17]>
#>  7 <int [0]>  <int [0]> 
#>  8 <int [0]>  <int [0]> 
#>  9 <int [25]> <int [24]>
#> 10 <int [24]> <int [23]>
#> 11 <int [11]> <int [10]>

# Remove those pair of nodes that could not be reached
paths %>% 
  filter(!lengths(edge_paths)==0)
#> # A tibble: 9 x 2
#>   node_paths edge_paths
#>   <list>     <list>    
#> 1 <int [20]> <int [19]>
#> 2 <int [14]> <int [13]>
#> 3 <int [10]> <int [9]> 
#> 4 <int [9]>  <int [8]> 
#> 5 <int [17]> <int [16]>
#> 6 <int [18]> <int [17]>
#> 7 <int [25]> <int [24]>
#> 8 <int [24]> <int [23]>
#> 9 <int [11]> <int [10]>

# Add columns with the `to` and `from` node index
paths %>% 
  rowwise() %>% 
  mutate(
    node_from = first(node_paths),
    node_to = last(node_paths)
  )
#> # A tibble: 11 x 4
#> # Rowwise: 
#>    node_paths edge_paths node_from node_to
#>    <list>     <list>         <int>   <int>
#>  1 <int [20]> <int [19]>         2     110
#>  2 <int [14]> <int [13]>         2     111
#>  3 <int [10]> <int [9]>          2     112
#>  4 <int [9]>  <int [8]>          2     113
#>  5 <int [17]> <int [16]>         2     114
#>  6 <int [18]> <int [17]>         2     115
#>  7 <int [0]>  <int [0]>         NA      NA
#>  8 <int [0]>  <int [0]>         NA      NA
#>  9 <int [25]> <int [24]>         2     118
#> 10 <int [24]> <int [23]>         2     119
#> 11 <int [11]> <int [10]>         2     120

# Filter only those paths that pass through node 3
paths %>% 
  filter(map_lgl(node_paths, ~3 %in% .))
#> # A tibble: 6 x 2
#>   node_paths edge_paths
#>   <list>     <list>    
#> 1 <int [10]> <int [9]> 
#> 2 <int [9]>  <int [8]> 
#> 3 <int [17]> <int [16]>
#> 4 <int [18]> <int [17]>
#> 5 <int [25]> <int [24]>
#> 6 <int [24]> <int [23]>