Mapping just one State of India and writing its name inside the state boundary

Question

I have downloaded gadm map for India (SpatialPolygonsDataFrame). When I use spplot it draws the complete map of India alongwith State boundaries.

A. Is it possible to just draw the boundary of one State (say, Assam) and not of others?

B. Can I write the names of States inside their respective boundaries?

C. Or suppose I want to color only one particular State and not others

Will be grateful for help. Thanks.

(A sample code is as below. But it plots full country and all States. What if I want only one State to be plotted inside the country)

library(sp)  
library(RColorBrewer)

load("IND_adm1.RData")
abc <- read.csv("crime.csv", header = TRUE)
temp <- abc[,c(1,4)]
State = temp[1:38,1]
Offence = temp[1:38,2]
afg <- data.frame(State, Offence)
gadm$Offence <- afg[1:35,]
col <- brewer.pal(n = 9, name = "OrRd")
spplot(gadm, "Offence", col.regions = col, at = c(0,50,100,200, 500,1000, 1500,2000,2500,4000), main = "Offence")

Answer 1

Let me apply the great lesson of @hrbrmstr to this case. You can learn a lot from him. The link is here.

library(raster)
library(rgdal)
library(rgeos)
library(ggplot2)
library(dplyr)

### Q1: Assam only

### Get data
india <- getData("GADM", country = "India", level = 1)

### Choose Assam
assam <- subset(india, NAME_1 == "Assam")

### SPDF to DF
map <- fortify(assam)

### Draw a map

ggplot() +
geom_map(data = map, map = map, aes(x = long, y = lat, map_id = id, group = group))

### Q2: State with their names

map <- fortify(india)
map$id <- as.integer(map$id)

dat <- data.frame(id = 1:(length(india@data$NAME_1)), state = india@data$NAME_1)
map_df <- inner_join(map, dat, by = "id")

centers <- data.frame(gCentroid(india, byid = TRUE))
centers$state <- dat$state


### This is hrbrmstr's own function
theme_map <- function (base_size = 12, base_family = "") {
theme_gray(base_size = base_size, base_family = base_family) %+replace% 
theme(
axis.line=element_blank(),
axis.text.x=element_blank(),
axis.text.y=element_blank(),
axis.ticks=element_blank(),
axis.ticks.length=unit(0.3, "lines"),
axis.ticks.margin=unit(0.5, "lines"),
axis.title.x=element_blank(),
axis.title.y=element_blank(),
legend.background=element_rect(fill="white", colour=NA),
legend.key=element_rect(colour="white"),
legend.key.size=unit(1.5, "lines"),
legend.position="right",
legend.text=element_text(size=rel(1.2)),
legend.title=element_text(size=rel(1.4), face="bold", hjust=0),
panel.background=element_blank(),
panel.border=element_blank(),
panel.grid.major=element_blank(),
panel.grid.minor=element_blank(),
panel.margin=unit(0, "lines"),
plot.background=element_blank(),
plot.margin=unit(c(1, 1, 0.5, 0.5), "lines"),
plot.title=element_text(size=rel(1.8), face="bold", hjust=0.5),
strip.background=element_rect(fill="grey90", colour="grey50"),
strip.text.x=element_text(size=rel(0.8)),
strip.text.y=element_text(size=rel(0.8), angle=-90) 
)   
}

ggplot() +
geom_map(data = map_df, map = map_df,
         aes(map_id = id, x = long, y = lat, group = group),
         color = "#ffffff", fill = "#bbbbbb", size = 0.25) +
geom_text(data = centers, aes(label = state, x = x, y = y), size = 2) +
coord_map() +
labs(x = "", y = "", title = "India State") +
theme_map()

### Q3: Add color to one state

### Create a column for color. Assam will have a different color.
map_df2 <- transform(map_df, hue = ifelse(state == "Assam", "a", NA))


ggplot() +
geom_map(data = map_df2, map = map_df2,
         aes(map_id = id, x = long, y = lat, group = group, fill = hue),
         color = "#ffffff", size = 0.25) +
geom_text(data = centers, aes(label = state, x = x, y = y), size = 2) +
coord_map() +
labs(x = "", y = "", title = "India State") +
theme_map() +
theme(legend.position = "none")