Vehicle Smog Comparison: Los Angeles vs Baltimore

library(ggplot2)

NEI <- readRDS("summarySCC_PM25.rds")
SCC <- readRDS("Source_Classification_Code.rds")

vehicles_SCC <- SCC[grep("Veh", SCC$SCC.Level.Two), ]$SCC

subset <- NEI[NEI$SCC %in% vehicles_SCC 
              & NEI$fips %in% c('24510', '06037'),]

subset$fips <- factor(subset$fips, c('24510', '06037'), 
                      labels=c('Baltimore', 'Los Angeles'))

agg_data <- aggregate(Emissions ~ fips + year, subset, FUN=mean)
mainplot <- ggplot(agg_data, aes(x=year, y=Emissions, color=fips)) + geom_line()
mainplot <- mainplot + ggtitle(bquote(PM[2.5] : " vehicle emissions by year by city")) 
print(mainplot)