Normalized Frequency of Terrorism in the US

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## Load libraries
library(ggplot2)
library(plyr)
library(maps)
library(stringr)

## Load terrorism data
gtd.data <- read.csv("gtd.csv", stringsAsFactors = F)



##
## Begin USA heatmap plot
##

## Subset data to only include terrorist attacks in the USA
gtd.usa <- subset(gtd.data, country_txt == "United States")

## Clean provstate column
gtd.usa$provstate <- str_replace(gtd.usa$provstate, "(U.S. State)", "")
gtd.usa$provstate <- str_replace(gtd.usa$provstate, "[(]", "")
gtd.usa$provstate <- str_replace(gtd.usa$provstate, "[)]", "")

## Trim whitespaces
gtd.usa$provstate <- str_trim(gtd.usa$provstate)

## Load US state population data
populations <- read.csv("states.csv")

## Create counts of terrorist activity in each state
counts <- count(gtd.usa, "provstate")

## Merge the populations dataset with the counts dataset
gtd.pop.merge <- merge(counts, populations, by.x = "provstate", by.y = "Name")

## Create normalized terrorism frequency by dividing frequency
## by the population of the state
gtd.pop.merge <- mutate(gtd.pop.merge, normal = freq / CENSUS2010POP)
gtd.pop.merge$normal <- log10(gtd.pop.merge$normal)

gtd.pop.merge$provstate <- tolower(gtd.pop.merge$provstate)
names(gtd.pop.merge)[1] <- "region"

## Load US state data
states <- map_data("state")

## Merge the map data with our previous dataset
merged <- merge(states, gtd.pop.merge, sort = FALSE, by = "region")

## Plot the heatmap
g <- ggplot(merged) + geom_polygon(aes(x = long, y = lat, group = group,
                                       fill = normal))

g <- g + scale_fill_gradient(low = "lightgreen", high = "blue")

g <- g + theme_bw() + labs(fill = "Normalized Frequency of Terrorism") +
     theme(legend.position = "bottom")

g <- g + xlab(NULL) + ylab(NULL)

g <- g + theme(panel.grid.minor=element_blank(),
               panel.grid.major=element_blank())

g <- g + theme(axis.text.x = element_blank(), axis.text.y = element_blank())

g <- g + ggtitle("Normalized Frequency of Terrorism in the USA")

g <- g + scale_x_continuous(breaks = NULL) + scale_y_continuous(breaks = NULL)

g