plot4.R

plot4<-function(){
	data<-read.table("household_power_consumption.txt", header=TRUE, sep=";", nrows=69520, colClasses="character")
	data<-data[66637:69516,]
	DateTime<-paste(data[,"Date"], data[,"Time"], sep=" ")
	DateTime<-strptime(DateTime, "%d/%m/%Y %X")
	data<-cbind(DateTime, data)
	data<-subset(data, select=-c(Date,Time))
	index<-2:8
	for(i in index){
		data[,i]<-as.numeric(data[,i])
	}
	
	par(mfrow = c(2,2))
	
	with(data, plot(DateTime, Global_active_power, type="l", xlab="", ylab="Global Active Power"))
	with(data, plot(DateTime, Voltage, type="l", xlab="datetime", ylab="Voltage"))
	
	with(data, plot(DateTime, Sub_metering_1, type="n", xlab="", ylab="Energy sub metering"))
	with(data, lines(DateTime, Sub_metering_1, type="l", col="black"))
	with(data, lines(DateTime, Sub_metering_2, type="l", col="red"))
	with(data, lines(DateTime, Sub_metering_3, type="l", col="blue"))
	legend("topright", bty="n", lty = "solid", col = c("black", "red", "blue"), legend = c("Sub_metering_1","Sub_metering_2", "Sub_metering_3"))

	with(data, plot(DateTime, Global_reactive_power, type="l", xlab="datetime", ylab="Global Reactive Power"))
	
	dev.copy(png, width=480, height=480, file = "plot4.png")
	dev.off()
	
}