How to plot regions in a country, each shaded by some corresponding value

Question

In particular I have a set of distinct regions in India, each with a "marketshare" value.

regions <- data.frame(Region=c("TELANGANA", "TAMIL NADU", "JAMMU & KASHMIR"), Marketshare=c(.25, .30, .15))
regions
           Region Marketshare
1       TELANGANA        0.25
2      TAMIL NADU        0.30
3 JAMMU & KASHMIR        0.15

I can plot India using ggmap real easily using

library(ggmap)
map <- get_map("India", zoom=6, maptype="toner-lite")
ggmap(map)

But how can I specifically include the regions in my dataset and shade each of them using the column Marketshare?

Note: I've seen this question and answer, but it seems overly complex for my needs and was wondering if there's any easier way.

Please show at least _some_ effort here. There are almost countless examples on SO showing how to read shapefiles and make choropleths. Linking to one overly-complex q/a doesn't absolve you from some effort. What research beyond one link on SO have you done and what did not work for your fairly straightforward requirements? — hrbrmstr, Nov 07 '15 at 02:34

jazzurro · Accepted Answer · 2015-11-07T03:00:04.273

As hrbrmstr mentioned, I think it would be great if you can show some efforts you made. Here, I created two maps. The first one is with ggmap, and the other with ggplot. In your example code, your map zoom was off in order to show all three regions you specified. So I revised your code. What you need on top of the map is polygons for the regions you want. In order to get them, you download data using get_data(). Then, you need to subset it. As the linked question showed, you need to go through a merge process in order to add marketshare to a final data frame. I collected id for each regions and created a data frame with marketshare, which is foo. temp is the final data frame which contains polygon information as well as marketshare. You use marketshare for fill and draw a map.

library(raster)
library(ggmap)
library(ggplot2)

### Get India data
india <- getData("GADM", country = "India", level = 2)

map <- get_map("India", zoom = 4, maptype = "toner-lite")
regions <- data.frame(Region=c("Telangana", "Tamil Nadu", "Jammu and Kashmir"), Marketshare=c(.25, .30, .15))

states <- subset(india, NAME_1 %in% regions$Region)

ind1 <- states$ID_2[states$NAME_1 == "Telangana"]
ind2 <- states$ID_2[states$NAME_1 == "Tamil Nadu"]
ind3 <- states$ID_2[states$NAME_1 == "Jammu and Kashmir"]

states <- fortify(states)

foo <- data.frame(id = c(ind1, ind2, ind3),
                  marketshare = rep(regions$Marketshare, times = c(length(ind1), length(ind2), length(ind3))))

temp <- merge(states, foo, by = "id")

ggmap(map) +
geom_map(data = temp, map = temp,
         aes(x = long, y = lat, map_id = id, group = group, fill = marketshare),
         colour = "grey50", size = 0.3) +
theme(legend.position = "none")

Alternatively, you can draw a map with ggplot so that you just show India only. In this case, you create a data frame from the download data, india. You draw India once, then you draw specific regions on top of the map. I converted marketshare to factor for colour reasons here.

india.map <- fortify(india)

ggplot() +
geom_map(data = india.map, map = india.map,
         aes(x = long, y = lat, map_id = id, group = group),
         colour = "grey50", size = 0.3) +
geom_map(data = temp, map = temp,
         aes(x = long, y = lat, map_id = id, group = group, fill = factor(marketshare)),
         colour = "grey50", size = 0.3) +
theme(legend.position = "none")

How to plot regions in a country, each shaded by some corresponding value

1 Answers1

Linked