plot2.r

# Exploratory Data Analysis -  
# Q.2. 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.

# upload data files
NEI <- readRDS("~/summarySCC_PM25.rds")
View(NEI)

SCC <- readRDS("~/Source_Classification_Code.rds")
View(SCC)

NEI_sampling <- NEI[sample(nrow(NEI), size=5000, replace=F), ]

MD <- subset(NEI, fips=='24510')

png(filename='~/plot2.png')

barplot(tapply(X=MD$Emissions, INDEX=MD$year, FUN=sum), 
        main='Total Emission in Baltimore City, MD', 
        xlab='Year', ylab=expression('PM'[2.5]))

dev.off()