get_spatial_link_dist_matrix.R

library(sfdep)
library(data.table)
library(cppRouting)

# get distance between neighbors
geo <- sf::st_geometry(guerry)
nb <- sfdep::st_contiguity(geo)
dists <- sfdep::st_nb_dists(geo, nb)

# fun to convert nb dist to a data.frame in long format
nb_list_to_df <- function(nb, dists) {
  
  mtrx <- sfdep::wt_as_matrix(nb, dists)
  
  matrix_length <- 1:length(mtrx[1,])
  
  # FULL MATRIX
  mtrx_long <- cbind(
    as.data.table(
      data.table::CJ(matrix_length, matrix_length)), # df two columns
    'dist' = as.vector(mtrx)  # matrix values in a vector
  )
  
  # keep only dist between neighbors
  mtrx_long <- subset(mtrx_long, dist >0)
  setnames(mtrx_long, c('from', 'to', 'dist'))
  
  return(mtrx_long)
}

# convert nb dist to a data.frame in long format
od_df <- nb_list_to_df(nb, dists)

# create graph
graph  <-  cppRouting::makegraph(od_df, directed = F)

# distances
dist_link <- cppRouting::get_distance_matrix(Graph=graph, 
                                             from = unique(od_df$from), 
                                             to = unique(od_df$from), 
                                             algorithm = 'mch')

head(dist_link)