Choropleth using ggplot2

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Choropleth using ggplot2

Richard Sherman
Hello all,

I am trying to plot a simple choropleth, something I’ve done a while ago using rworldmap and also (if I recall correctly) ggplot2, but I am failing to draw the map at all and failing (I think) to merge my data properly with the shapefile. Thank you for help with a basic question. I’d like to know what is wrong with what I’m doing here.

I posted this to r-sig-geo but received no responses.

My R script is

library(ggplot2)
library(rgdal)
library(plyr)

# get shapefile for world map
download.file("https://opendata.arcgis.com/datasets/252471276c9941729543be8789e06e12_0.zip", destfile = "countries.zip”)

# get world bank maternal mortality data
download.file("http://api.worldbank.org/v2/en/indicator/SH.STA.MMRT?downloadformat=csv", destfile = "mmr.zip”)

# get csv file with concordance between ISO-2-alpha and ISO-3-alpha country codes
download.file("https://raw.githubusercontent.com/rsspdx/mmr/master/iso_2_iso_3.csv", destfile = "iso_2_iso_3.csv”)

# unzip the zipped files
mmr.files <- unzip("mmr.zip")
unzip("countries.zip”)

# read in maternal mortality data and fix it up
mmr.data <- read.csv(mmr.files[2], skip = 3, stringsAsFactors = FALSE)
mmr.data.name <- mmr.data$Country.Name
mmr.data.code <- mmr.data$Country.Code
mmr.data.mmr <- mmr.data$X2015
mmr.data.df <- as.data.frame(cbind(mmr.data.name, mmr.data.code, mmr.data.mmr))
names(mmr.data.df) <- c("Country.Name", "Country.Code", "mmr”)

# read in the shapefile
world.map <- readOGR(dsn=".", layer = "UIA_World_Countries_Boundaries")

# --------- possibly I should be doing this ------------
#
# world.map@data$id <- rownames(world.map@data)
# world.map.df <- fortify(world.map)
#
# -------------------------------------------------------

#------or perhaps I need to merge the data into a slot of the shapefile
#------but I can’t recall (or never knew?) how to do that

# get ISO2 country codes
iso_2_iso_3 <- read.csv("iso_2_iso_3.csv”)

# ISO2 in this file is called ISO in the shapefile, create ISO variable
# then merge into mmr.data
iso_2_iso_3$ISO <- iso_2_iso_3$ISO2
mmr.data.df <- merge(iso_2_iso_3, mmr.data.df, by.x="ISO3", by.y="Country.Code”)

# merge maternal mortality data into shapefile
mmr <- merge(world.map, mmr.data.df, by = "ISO")
mmr <- fortify(mmr)
str(mmr)

# ---------create a map, not working
map <- ggplot(data = mmr, aes(x = long, y = lat, group = group))

# ---------look at the map, obviously not working
map + geom_polygon(fill = mmr$mmr)

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