Create sf Lines from Start and End Coordinates

Posted on 2 mins read

As I couldn’t believe it myself, but there’s not a developed function in R that creates a sf object that contains several lines, deriving from the start and end coordinates (latitude and longitude) of each line. For example, I have a simple table with the line id and start and end point coordinates, like this:

Pair_ID O_Lat O_Lon D_Lat D_Lon
1 47.6408 -122.3359 47.6911 -122.4516
2 47.6081 -122.0917 47.5152 -122.2197
3 47.7023 -122.2591 47.6526 -122.2096

Then, I created a function to convert this table into a single sf object that contains three lines:


library(dplyr)
library(sf)
library(sp)
library(leaflet)

###The table above is imported as "od" here.


od_coords_to_sf <- function(df) {
  #prepare the table from wide to long
  
  part1 <-df[,c(1,2,3)]  %>%
    mutate(shape_pt_sequence =1)%>%
    rename(shape_pt_lat=O_Lat,
           shape_pt_lon=O_Lon)
  
  part2 <-df[,c(1,4,5)]  %>%
    mutate(shape_pt_sequence =2)%>%
    rename(shape_pt_lat=D_Lat,
           shape_pt_lon=D_Lon)
  
  allpart <- rbind(part1, part2)
  allpart<-allpart %>% arrange(colnames(df[1]))
  m <- as.matrix(allpart[order(allpart$shape_pt_sequence),
                    c("shape_pt_lon", "shape_pt_lat")])
  m <- sf::st_linestring(m)
  shape_linestrings <- sf::st_sfc(m, crs = 4326)
  shapes_sf <- sf::st_sf(Pair_ID =allpart$Pair_ID, geometry = shape_linestrings)
  shapes_sf <-shapes_sf %>% distinct(Pair_ID, .keep_all = TRUE)
  return(shapes_sf)
}


#Now run a loop to go through all the pt pairs


#run loop

all_segment <- data.frame()

for (i in 1:nrow(od)){
  one_seg <- od[i,] %>% od_coords_to_sf()
  all_segment <- rbind(all_segment, one_seg)
}

plot(all_segment)

#map the segments using leaflet

map <- leaflet(data=all_segment)%>% addTiles()%>% addPolylines()

map

And the final results look like:

And, the end, tada!

P.S. I recently came up with this page talking about converting text strings directly to sf. If this works it would be so much simpler than the method above. However, I haven’t been able to successfully run it. Will continue to test this out.