Creating Heatmaps

STEP 1: READ IN THE DATA

Get the data - I’ve just got it downloaded locally. Also - load the required libraries for the mapping.

library(ggplot2)        ## VISUALIZATIONS
library(ggmap)          ## MAPS

## READ IN THE DATA 
conc_deaths <- read.csv("Accidental_Drug_Related_Deaths_January_2012-Sept_2015.csv")

STEP 2: CLEAN THE DATA

The location data, in the deathLoc column, is ugly. It comes in this format:

To clean it, I first do a substitution for the ‘’ into a ‘;’. R was throwing errors when I tried to just split on ‘’. I then split the data on the ‘;’.

## SUBSTITUTE '\n' FOR ';'
loc_data <- gsub(pattern = "\n", replacement = ";", x = conc_deaths$DeathLoc)
## SPLIT ON ';'
loc_data <- strsplit(loc_data, ";")

I then add the town and cordinates to the initial dataset as separate columns and blow away the loc_data list and the original DeathLoc column (just a couple clean up steps).

## FOR EACH ROW, ADD THE TOWN TO THE TOWN COLUMN 
## AND COORDINATES TO THE COORDINATES COLUMN
for(i in 1:length(loc_data)){
        conc_deaths$town[i] <- loc_data[[i]][1]
        conc_deaths$coordinates[i] <- loc_data[[i]][2]
}

## BLOW AWAY THE NOW UNNEEDED VARIABLES
loc_data <- NULL
conc_deaths$DeathLoc <- NULL

Now we need to clean up the coordinates column and split it into a latitude and longitude. I then add them to their own columns

## REMOVE THE '(' 
conc_deaths$coordinates <- gsub(pattern = "\\(", replacement = "", 
                          x = conc_deaths$coordinates)
## REMOVE THE ')' 
conc_deaths$coordinates <- gsub(pattern = ")", replacement = "", 
                          x = conc_deaths$coordinates)

## SPLIT ON THE ','
loc_data <- strsplit(conc_deaths$coordinates, split = ", ")

## FOR EACH ROW, ADD THE LATITUDE TO THE LAT COLUMN 
## AND LONGITUDE TO THE LON COLUMN
for(i in 1:length(loc_data)){
        conc_deaths$lat[i] <- loc_data[[i]][1]
        conc_deaths$lon[i] <- loc_data[[i]][2]
}

Final clean up step before we map - we need to change the lat and lon columns to numerics - by default they are factors. Also, unnecessarily, I am blowing away the unneeded variables.

## CHANGE THE VARIABLE TO NUMERICS
conc_deaths$lat <- as.numeric(conc_deaths$lat)
conc_deaths$lon <- as.numeric(conc_deaths$lon)

## GET RID OF THE UNNECESSARY VARIABLES
loc_data <- NULL
conc_deaths$coord <- NULL

MAPPING THE DATA

Finally, we are ready to map the data!

Here we get the map of Conneticut (I do it for 2 levels of zoom), and then map it! The higher level of zoom gives you this map:

## GET THE BASE MAP
con <- get_map(location = "Conneticut", maptype = "roadmap", zoom = 8)

## Map from URL : http://maps.googleapis.com/maps/api/staticmap?center=Conneticut&zoom=8&size=640x640&scale=2&maptype=roadmap&language=en-EN&sensor=false

## Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Conneticut&sensor=false

## ADD THE "HEAT" TO THE MAP
map1 <- ggmap(con, extent = "device") + geom_density2d(data = conc_deaths, 
                                                        aes(x = lon, y = lat)) + 
        stat_density2d(data = conc_deaths, aes(fill = ..level.., alpha = ..level..),
                       size = 0.01, geom = "polygon") + 
        scale_fill_gradient(low = "green", high = "red", guide = FALSE) + 
        scale_alpha(range = c(0, 0.3), guide = FALSE)

## DISPLAY IT
map1

## Warning: Removed 187 rows containing non-finite values (stat_density2d).

## Warning: Removed 187 rows containing non-finite values (stat_density2d).

The next higher zoom gives you this map:

## GET THE BASE MAP
con1 <- get_map(location = "Conneticut", maptype = "roadmap", zoom = 9)

## Map from URL : http://maps.googleapis.com/maps/api/staticmap?center=Conneticut&zoom=9&size=640x640&scale=2&maptype=roadmap&language=en-EN&sensor=false

## Information from URL : http://maps.googleapis.com/maps/api/geocode/json?address=Conneticut&sensor=false

## ADD THE "HEAT" TO THE MAP
map2 <- ggmap(con1, extent = "device") + geom_density2d(data = conc_deaths, 
                                                        aes(x = lon, y = lat)) + 
        stat_density2d(data = conc_deaths, aes(fill = ..level.., alpha = ..level..),
                       size = 0.01, geom = "polygon") + 
        scale_fill_gradient(low = "green", high = "red", guide = FALSE) + 
        scale_alpha(range = c(0, 0.3), guide = FALSE)

## DISPLAY IT
map2

## Warning: Removed 426 rows containing non-finite values (stat_density2d).

## Warning: Removed 426 rows containing non-finite values (stat_density2d).