plot4.R

library(ggplot2)
library(sqldf)
library(scales)

## This first line will likely take a few seconds. Be patient!
NEI <- readRDS("summarySCC_PM25.rds")
SCC <- readRDS("Source_Classification_Code.rds")

colnames(NEI)
head(NEI, n=1)
str(unique(NEI$type))

colnames(SCC)
str(unique(SCC$EI.Sector))
summary(SCC)

which(duplicated(SCC$SCC) == T)

p25 <- sqldf('SELECT n.year, n.type,
              sum(n.Emissions) as emissions
              FROM NEI n
              JOIN SCC s ON (n.SCC = s.SCC)
              WHERE s.`EI.Sector` like "Fuel Comb%Coal"
              GROUP BY year, type')

p25_plot <-
   ggplot(p25, aes(x = factor(year), y = emissions, fill = type)) +
   geom_bar(stat = "identity", colour="grey50") +
   scale_y_continuous(labels = comma) +
   geom_smooth(method = "auto", se=F, aes(group=1), color="yellow") +
   xlab("Year") + ylab("Total emissions")

suppressMessages(print(p25_plot))