Lines on Maps in R

How to draw lines, great circles, and contours on maps in R. Lines on maps can show distance between geographic points or be contour lines (isolines, isopleths, or isarithms).

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Flight Paths Map

library(plotly)
library(dplyr)
# airport locations
air <- read.csv('https://raw.githubusercontent.com/plotly/datasets/master/2011_february_us_airport_traffic.csv')
# flights between airports
flights <- read.csv('https://raw.githubusercontent.com/plotly/datasets/master/2011_february_aa_flight_paths.csv')
flights$id <- seq_len(nrow(flights))

# map projection
geo <- list(
  scope = 'north america',
  projection = list(type = 'azimuthal equal area'),
  showland = TRUE,
  landcolor = toRGB("gray95"),
  countrycolor = toRGB("gray80")
)

fig <- plot_geo(locationmode = 'USA-states', color = I("red"))
fig <- fig %>% add_markers(
  data = air, x = ~long, y = ~lat, text = ~airport,
  size = ~cnt, hoverinfo = "text", alpha = 0.5
)
fig <- fig %>% add_segments(
    data = group_by(flights, id),
    x = ~start_lon, xend = ~end_lon,
    y = ~start_lat, yend = ~end_lat,
    alpha = 0.3, size = I(1), hoverinfo = "none"
  )
fig <- fig %>% layout(
    title = 'Feb. 2011 American Airline flight paths<br>(Hover for airport names)',
    geo = geo, showlegend = FALSE, height=800
  )

fig

London to NYC Great Circle

library(plotly)

fig <- plot_geo(lat = c(40.7127, 51.5072), lon = c(-74.0059, 0.1275))
fig <- fig %>% add_lines(color = I("blue"), size = I(2))
fig <- fig %>% layout(
    title = 'London to NYC Great Circle',
    showlegend = FALSE,
    geo = list(
      resolution = 50,
      showland = TRUE,
      showlakes = TRUE,
      landcolor = toRGB("grey80"),
      countrycolor = toRGB("grey80"),
      lakecolor = toRGB("white"),
      projection = list(type = "equirectangular"),
      coastlinewidth = 2,
      lataxis = list(
        range = c(20, 60),
        showgrid = TRUE,
        tickmode = "linear",
        dtick = 10
      ),
      lonaxis = list(
        range = c(-100, 20),
        showgrid = TRUE,
        tickmode = "linear",
        dtick = 20
      )
    )
  )

fig

Contour lines on globe

df <- read.csv('https://raw.githubusercontent.com/plotly/datasets/master/globe_contours.csv')
df$id <- seq_len(nrow(df))

library(tidyr)
d <- df %>%
  gather(key, value, -id) %>%
  separate(key, c("l", "line"), "\\.") %>%
  spread(l, value)

geo <- list(
  showland = TRUE,
  showlakes = TRUE,
  showcountries = TRUE,
  showocean = TRUE,
  countrywidth = 0.5,
  landcolor = toRGB("grey90"),
  lakecolor = toRGB("white"),
  oceancolor = toRGB("white"),
  projection = list(
    type = 'orthographic',
    rotation = list(
      lon = -100,
      lat = 40,
      roll = 0
    )
  ),
  lonaxis = list(
    showgrid = TRUE,
    gridcolor = toRGB("gray40"),
    gridwidth = 0.5
  ),
  lataxis = list(
    showgrid = TRUE,
    gridcolor = toRGB("gray40"),
    gridwidth = 0.5
  )
)

fig <- plot_geo(d)
fig <- fig %>% group_by(line)
fig <- fig %>% add_lines(x = ~lon, y = ~lat)
fig <- fig %>% layout(
    showlegend = FALSE, geo = geo,
    title = 'Contour lines over globe<br>(Click and drag to rotate)'
  )

fig

What About Dash?

Dash for R is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.

Learn about how to install Dash for R at https://dashr.plot.ly/installation.

Everywhere in this page that you see fig, you can display the same figure in a Dash for R application by passing it to the figure argument of the Graph component from the built-in dashCoreComponents package like this:

library(plotly)

fig <- plot_ly() 
# fig <- fig %>% add_trace( ... )
# fig <- fig %>% layout( ... ) 

library(dash)
library(dashCoreComponents)
library(dashHtmlComponents)

app <- Dash$new()
app$layout(
    htmlDiv(
        list(
            dccGraph(figure=fig) 
        )
     )
)

app$run_server(debug=TRUE, dev_tools_hot_reload=FALSE)