plot5.R

#Reference UDFs
source("./udf.R")

#Define function for building the plot png file
plot5 <- function(dframes=NULL){
	packages <- c("dplyr","ggplot2","sqldf")
	packagechecks <- checkPackages(packages)

	if(is.null(dframes)){
		dframes <- loaddata()
	}

	pmdf <- data.frame(dframes[1])
	summary <- data.frame(dframes[2])

#Begin Analysis
	summary.baltimore <- subset(summary, summary$fips == "24510")

	scc.mobile <- unlist(sqldf('Select "SCC" 
		from pmdf 
		where "SCC.Level.One" = "Mobile Sources" 
		order by "SCC"'))
	summary.mobile <- summary.baltimore[summary.baltimore$SCC %in% scc.mobile 
		& summary.baltimore$type=="ON-ROAD", ]

	mobile.by.year <- aggregate(summary.mobile$Emissions, 
		by = list(summary.mobile$year), 
		FUN = "sum")

	mobile.by.year <- dplyr::rename(mobile.by.year, 
		yr = Group.1, 
		pm25 = x)


	# Set bg color transparent
	par(bg = "transparent")

	# Start device
	png(file = "plot5.png", width=1200, height=800)

	# Draw plot 5
	print({
		qplot(yr, pm25, 
			data = mobile.by.year, 
			geom = c("point","smooth"), 
			method = "lm")
		})
	# Close the device
	dev.off()

	#Answer, They have decreased with the largest decrease from 1999 - 2002
}
#Call the Function
plot5()