R: Connecting Dots on a Map

Question

I am working with the R programming language.

Using the "leaflet" library, I made the following map for these 5 cities:

 library(dplyr) library(leaflet) map_data <- data.frame("Lat" = c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629), "Long" = c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957 ), type = c(1,2,3,4,5)) map_data$type = as.factor(map_data$type) leaflet(map_data) %>% addTiles() %>% addCircleMarkers(stroke = FALSE, label = ~type,fillOpacity = 0.8, labelOptions = labelOptions(direction = "center",style = list('color' = "white"),noHide = TRUE, offset=c(0,0), fill = TRUE, opacity = 1, weight = 10, textOnly = TRUE))

On this above map that I have created , I would now like to "connect" all these "points" (ie cities) on the map (in a route) based on their "number" (eg connect 1 with 2, 2 with 3, 3 with 4, 4 with 5, 5 with 1), and output the "total distance" of the route. I found a previous post that shows how to do this: How to show path and distance on map with leaflet, shiny apps?

I tried to adapt the code from this post to suit my question:

 library(osrm) route = osrmRoute(c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957 ), c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629), overview = 'full') route_summary = osrmRoute(c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957 ), c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629), overview = FALSE) leaflet() %>% addTiles() %>% addCircleMarkers(c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957 ), c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629), stroke = FALSE, label = ~type,fillOpacity = 0.8, labelOptions = labelOptions(direction = "center",style = list('color' = "white"),noHide = TRUE, offset=c(0,0), fill = TRUE, opacity = 1, weight = 10, textOnly = TRUE)) %>% addPolylines(route$lon,route$lat, label = paste(round(route_summary[1]/60), 'hr - ', round(route_summary[2]), 'km'), labelOptions = labelOptions(noHide = TRUE))

But this returns the following error:

 Error in UseMethod("metaData"): no applicable method for 'metaData' applied to an object of class "NULL"

Can someone please show me how to fix this problem?

I would like to do this using "leaflet" and not using "rshiny". In the end, I would like the final map to look something like this (this is supposed to represent a "single path" from a Travelling Salesman Problem):

[ [enter image description here][2]][2]

Note: I am starting to think that problem might be that the "osrmRoute()" function might not be able to work for more than 2 points?

• https://github.com/riatelab/osrm/issues/41
• https://rdrr.io/cran/osrm/man/osrmTrip.html

Answer 1

One way is for you to make API call:

https://github.com/Project-OSRM/osrm-backend/blob/master/docs/http.md

I'll just outline how can you do it:

data

df <- data.frame( lon = c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957), lat = c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629) )

url call

root <- "http://router.project-osrm.org/route/v1/driving/" options <- c( continue_straight = "true", overview = "full", annotations = "true", steps = "true" ) coords <- df %>% slice(c(seq_len(n()), 1)) %>% pmap_chr(str_c, sep = ",") %>% str_c(collapse = ";") options <- options %>% imap_chr(~str_c(.y, "=",.x)) %>% str_c(collapse = "&") %>% str_c("?",.) res <- rjson::fromJSON(file = str_c(root, coords, options))

Note that I've added first point as 6th row to make circle route.

map

 res$routes[[1]]$geometry %>% googlePolylines::decode() %>%.[[1]] %>% leaflet() %>% addTiles() %>% addPolylines(lng = ~lon, lat = ~lat) %>% addCircleMarkers( data = df, stroke = FALSE, label = seq_len(nrow(df)), fillOpacity = 0.8, labelOptions = labelOptions( direction = "center", style = list('color' = "white"), noHide = TRUE, offset=c(0,0), fill = TRUE, opacity = 1, weight = 10, textOnly = TRUE ) )

distance

res$routes[[1]]$distance

This is in meters (documentation)

EDIT

There probably is better way of labeling polyline but I don't have time now:

 library(sf) segment_df <- df %>% rbind(df[1,]) d <- segment_df %>% st_as_sf(coords = c("lon", "lat"), crs = 4326) %>% {st_distance(.[-6,],.[-1,], by_element = TRUE)} %>% as.vector() %>% round() m <- leaflet() %>% addTiles() for(i in seq_len(nrow(segment_df) - 1)) m <- m %>% addPolylines( data = segment_df[i:(i+1),], lng = ~lon, lat = ~lat, color = "red", label = paste(d[[i]], "m"), labelOptions(noHide = TRUE, direction = 'top') ) m <- m %>% addCircleMarkers( data = df, stroke = FALSE, label = seq_len(nrow(df)), fillOpacity = 0.8, labelOptions = labelOptions( direction = "center", style = list('color' = "white"), noHide = TRUE, offset=c(0,0), fill = TRUE, opacity = 1, weight = 10, textOnly = TRUE ) )

If you want only to show total distance then that is easier and does not require loop, just replace loop with:

 segment_df %>% leaflet() %>% addTiles() %>% addPolylines( lng = ~lon, lat = ~lat, color = "red", label = paste(sum(d), "m"), labelOptions = labelOptions(noHide = TRUE, direction = 'top') )

I hope you understand (and see from map) that this is not drivable.

Answer 2

Here is an answer I tried based on @det's answer:

 library(sf) library(geosphere) library(dplyr) library(leaflet) library(data.table) library(VPF) #add a 6th row that is equal to the 1st row - so that the path loops back map_data <- data.frame("Lat" = c(43.6426, 43.6424, 43.6544, 43.6452, 43.6629, 43.6426), "Long" = c(-79.3871, -79.3860, -79.3807, -79.3806,-79.3957, -79.3871 ), type = c(1,2,3,4,5,1)) map_data$type = as.factor(map_data$type) m1 = leaflet(map_data) %>% addTiles() %>% addCircleMarkers(stroke = FALSE, label = ~type,fillOpacity = 0.8, color = ~ifelse(type==1,"red","blue"), labelOptions = labelOptions(direction = "center",style = list('color' = "white"), noHide = TRUE, offset=c(0,0), fill = TRUE, opacity = 1, weight = 10, textOnly = TRUE)) m1 %>% addTiles() %>% addPolylines(data = map_data, lng = ~Long, lat = ~Lat, group = ~type)

Now, I want to calculate the total distance of the trip and have it displayed on the map:

 #distances (https://stackoverflow.com/questions/42119438/calculate-distance-between-two-long-lat-coordinates-in-a-dataframe) result = rbind( cbind(map_data[1:nrow(map_data)-1,c(1,2)], map_data[-1,c(1,2)]), cbind(map_data[nrow(map_data), c(1,2)], map_data[1,c(1,2)]) ) colnames(result) <- c("start_lat", "start_long", "end_lat", "end_long") result$id = as.factor(c(1,2,3,4,5,1)) result = data.frame(result) for (i in 1:nrow(result)) { a<-result$start_long[i] b<-result$start_lat[i] c<-result$end_long[i] d<-result$end_lat[i] result$distance[i]<-distm(c(a,b),c(c,d), fun = distHaversine) } #total distance of trip in meters d = result$distance total_d = signif(sum(d),3) m1 %>% addPolylines( data = map_data, lng = ~Long, lat = ~Lat, color = "blue", label = paste0(total_d, " meters"), labelOptions(noHide = TRUE, direction = 'top') )

I think I finally got it - thanks so much @ Det