Map Lines from Points

This code provides an example where you can take a CSV of points with a unique ID for each line (I use the ids “one” and “two” to map two lines), and map them with Leaflet in R. You could use rgdal to save these as GeoJSON or Shapefile or any other spatial format.

1 Load Libraries

library(leaflet)
library(sp)

2 Load sample points

Here I load the sample points posted on stack overflow. Then I randomly assign each point to be either in line “one” or line “two”

d <- read.csv("./sample-points2.csv")

d$id <- data.frame(id = factor(
                              ifelse(runif(dim(d)[1]) > 0.75, "one", "two"),
                              c("one", "two")
                            ))

head(d)

##   longitude latitude  id
## 1 -119.2875 37.16585 two
## 2 -119.2875 37.16497 one
## 3 -119.2875 37.16497 two
## 4 -119.2875 37.16497 two
## 5 -119.2875 37.16585 two
## 6 -119.2875 37.16497 one

3 Turn the points into a SpatialPointsDataFrame

d <- SpatialPointsDataFrame(coords=d[,1:2],
                            data = d[,3])

summary(d)

## Object of class SpatialPointsDataFrame
## Coordinates:
##                  min        max
## longitude -119.28760 -119.28718
## latitude    37.16478   37.16585
## Is projected: NA 
## proj4string : [NA]
## Number of points: 74
## Data attributes:
##    id    
##  one:18  
##  two:56

4 Map Initial Points

Here is a map of the inital points

basemap <- leaflet() %>% addProviderTiles("Esri.WorldImagery", options = tileOptions(maxZoom = 22))
basemap %>% addCircleMarkers(data=d)

5 Make SpatialLinesDataFrame from lines

first this code subsets the two lines. Then it turns these lines into a SpatialLinesDataFrame

d1 <- subset(d, d@data$id=="one")
d2 <- subset(d, d@data$id=="two")


Sl1 = Line(d1)
Sl2 = Line(d2)
S1 = Lines(list(Sl1), ID="one")
S2 = Lines(list(Sl2), ID="two")
Sl = SpatialLinesDataFrame(SpatialLines(list(S1,S2)),
                           data=data.frame(id=c("one","two")),
                           match.ID=FALSE)

6 Map the resulting lines

The code assigns different line colors to each line and then maps them again using Leaflet

lineColor <- colorFactor(rainbow(length(Sl@data$id)) , Sl@data$id)
basemap %>% addPolylines(data=Sl, color= ~lineColor(id))