plot2.R

NEI <- readRDS("summarySCC_PM25.rds")
SCC <- readRDS("Source_Classification_Code.rds")
# Have total emissions from PM2.5 decreased in the Baltimore City, Maryland (fips == "24510") from 1999 to 2008? Use the base plotting system to make a plot answering this question.
subsetNEI  <- NEI[NEI$fips=="24510", ]
aggregatedTotalxYear <- aggregate(Emissions ~ year, subsetNEI, sum)
png('plot2.png')
barplot(height=aggregatedTotalxYear$Emissions, names.arg=aggregatedTotalxYear$year, xlab="years", ylab=expression('total PM'[2.5]*' emission'),main=expression('Total PM'[2.5]*' in the Baltimore City, MD emissions at various years'))
dev.off()