plot3.R

 # Plot3

#Import dataset in R
df<-read.table(file="./household_power_consumption.txt",
               sep=";",header=TRUE,na.strings="?",stringsAsFactor=FALSE)

#Subset dataset for only dates 1/2/2007 and 2/2/2007
df.sub<-subset(df,Date %in% c("1/2/2007","2/2/2007"))

#Make new variable from Date and Time as POSIXlt class
df.sub$DateTime<-as.POSIXlt(strptime(paste(df.sub$Date,df.sub$Time),format="%d/%m/%Y %H:%M:%S"))

#Plot 3
png("./plot3.png",width=480,height=480)
plot(df.sub$DateTime,df.sub$Sub_metering_1,type="l",col="black",
     xlab="",ylab="Energy sub metering")
lines(df.sub$DateTime,df.sub$Sub_metering_2,col="red")
lines(df.sub$DateTime,df.sub$Sub_metering_3,col="blue")
legend("topright",lty=1,col=c("black","red","blue"),
       c("Sub_metering_1","Sub_metering_2","Sub_metering_3"))
dev.off()