Leaflet of Violent Crime Rates by State

23 Feb 2017

The map below is an example of using the leaflet R package to demonstrate statistics about a location (in this example, by state). There are a few great tutorials on leaflet and creating something useful and beautiful is fairly simple. I’ve adapted the code from https://rstudio.github.io/leaflet/choropleths.html for the mapping. The R code to create it is below the figure.

For this map, the violent crime rate per 100,000 individuals by state in 2015 is highlighted. Several aspects are nice: we combined our data with the mapping features of MapBox, we can see the statistics by having the mouse over the map, and it looks aesthetically nice.

library(leaflet)
library(sp)
library(tidyverse)

## The geo data for the states
## from http://eric.clst.org/Stuff/USGeoJSON
states <- geojsonio::geojson_read("us-states.geojson", what = "sp")

## Crime statistics from the FBI
## https://ucr.fbi.gov/crime-in-the-u.s/2015/crime-in-the-u.s.-2015/tables/table-5
crimes <- read.csv("FBI_crime.csv") %>%
  filter(Area == "State Total") %>%
  filter(type == "Rate per 100,000 inhabitants") %>%
  mutate(State = toupper(State)) %>%
  select(State, violent, murder) %>%
  mutate(State = gsub("[0-9]", "", State)) %>%
  data.frame

## Combine crime stats with the geo data
states2 = states
states2@data = states@data %>%
  mutate(State = toupper(NAME)) %>%
  left_join(crimes, by = "State") %>%
  data.frame

## The map
bins <- c(seq(100,800,100))
pal <- colorBin("YlOrRd", domain = states2$violent, bins = bins)

labels <- sprintf(
  "<strong>%s</strong><br/>%g violent crimes per\n100,000 individuals",
  states2$State, states2$violent
) %>% lapply(htmltools::HTML)

leaflet(states2) %>%
  setView(-96, 37.8, 4) %>%
  addProviderTiles(provider = "MapBox", options = providerTileOptions(
    id = "mapbox.light",
    accessToken = 'Your Own Token')) %>%
  addPolygons(
    fillColor = ~pal(violent),
    weight = 2,
    opacity = 1,
    color = "white",
    dashArray = "3",
    fillOpacity = 0.7,
    highlight = highlightOptions(
      weight = 5,
      color = "#666",
      dashArray = "",
      fillOpacity = 0.7,
      bringToFront = TRUE),
    label = labels,
    labelOptions = labelOptions(
      style = list("font-weight" = "normal", padding = "3px 8px"),
      textsize = "15px",
      direction = "auto")) %>%
  addLegend(pal = pal, 
            values = ~violent, 
            opacity = 0.7, 
            title = "Violent Crimes per 100,000",
            position = "bottomright")

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