task4.txt

library(dplyr)
library(ggplot2)
NEI <- readRDS("summarySCC_PM25.rds")
SCC <- readRDS("Source_Classification_Code.rds")
list<-grep("Fuel Comb.*Coal",SCC$EI.Sector)
list2<-SCC[list,]
list3<-list2$SCC
task4<-subset(NEI,SCC %in% list3)
df<-tbl_df(task4)
task4<-group_by(df,year)
a<-summarize(task4,total=sum(Emissions))
s<-as.data.frame(a)
png("plot4.png")
barplot(s$total,s$year,names=s$year,xlab="Years",ylab="Total Emissions",main="Total PM25 emissions from all years through coal and comb sources",col="pink")
dev.off()