Thematic Interactive Map

Last week all the #rstatsosphere see a beautiful swiss map from Timo Grossenbacher using just ggplot2. Now is the turn of highcharter because all can be better with a bit of interactivity.
maps
data-visualization
highcharts
minipost
Author

Joshua Kunst Fuentes

Published

January 20, 2017

The last month, yep, the past year I’ve working on create maps easily with highcharter, so when I saw this chart I took as challege!

Challenge accepted. it’s gonna be legen… – Me.

Packages and Data

The data used for this chart is the same using by Timo. But the workflow was slightly modified:

  1. Read the shapefile with maptools::readShapeSpatial.
  2. Simplify the shapefile (optional step) using rmapshaper::ms_simplify.
  3. Then transform the map data to geojson using geojsonio::geojson_list.
Code
library(tidyverse)
library(rmapshaper)
library(maptools)
library(highcharter)
library(geojsonio)
library(viridis)

shape <- here::here("posts", "2017-01-05-thematic-interactive-map", "data", "gde-1-1-15.shp")
map <- readShapeSpatial(shape)
map <- ms_simplify(map, keep = 1) # because ms_simplify fix the ü's
map <- geojson_list(map)

# this was to put the name on the tooltip
map$features <- map(map$features, function(x) {
  x$properties$name <- x$properties[["Secondary_"]] 
  x
})

data <- read_csv(here::here("posts", "2017-01-05-thematic-interactive-map", "data", "avg_age_15.csv"))
data <- select(data, -1)
data <- rename(data, value = avg_age_15)

# colors
no_classes <- 6

colors <- magma(no_classes + 2) %>% 
  rev() %>% 
  head(-1) %>% 
  tail(-1) %>% 
  gsub("FF$", "", .)

brks <- c(min(data$value), c(40,42,44,46,48), max(data$value))
brks <- ifelse(1:(no_classes + 1) < no_classes, floor(brks), ceiling(brks))

Map

Create the raw map is straightforward. The main challege was replicate the relief feature of the orignal map. This took some days to figure how add the backgound image. I did almost lost the hope but you know, new year, so I tried a little more and it was possible :):

  1. First I searched a way to transform the tif image to geojson. I wrote a mail @frzambra a geoRexpert :D. and he kindly said me that I was wrong. And he was right. NEXT!
  2. I tried with use divBackgroundImage but with this the image use all the container… so… NEXT.
  3. Finally surfing in the web I met plotBackgroundImage argument in highcharts which is uesd to put and image only in plot container (inside de axis) and it works nicely. It was necessary hack the image using the preserveAspectRatio (html world) to center the image but nothing magical.
Code
urlimage <- "https://raw.githubusercontent.com/jbkunst/r-posts/master/061-beautiful-thematic-maps-with-ggplot2-highcharter-version
/02-relief-georef-clipped-resampled.jpg"

hc <- highchart(type = "map") %>% 
  # data part
  hc_add_series(
    mapData = map, data = data, type = "map",
    joinBy = c("BFS_ID", "bfs_id"), value = "value",
    borderWidth = 0
    ) %>% 
  hc_colorAxis(dataClasses = color_classes(brks, colors)) %>% 
  # functionality
  hc_tooltip(
    headerFormat = "",
    pointFormat = "{point.name}: {point.value}",
    valueDecimals = 2
    ) %>% 
  hc_legend(
    align = "right",
    verticalAlign = "bottom",
    layout = "vertical",
    floating = TRUE
    ) %>%
  hc_mapNavigation(enabled = FALSE) %>% # if TRUE to zoom the relief image dont zoom.
  # info
  hc_title(text = "Switzerland's regional demographics") %>% 
  hc_subtitle(text = "Average age in Swiss municipalities, 2015") %>% 
  hc_credits(
    enabled = TRUE,
    text = "Map CC-BY-SA; Author: Joshua Kunst (@jbkunst) based mostly on Timo Grossenbacher (@grssnbchr) work, Geometries: ThemaKart, BFS; Data: BFS, 2016; Relief: swisstopo, 2016"
    ) %>% 
  # style
  hc_chart(
    plotBackgroundImage = urlimage,
    backgroundColor = "transparent",
    events = list(
      load = JS("function(){ $(\"image\")[0].setAttribute('preserveAspectRatio', 'xMidYMid') }")
      )
    )

hc