plot4.R

png("plot4.png", width=480, height=480)
par(mfrow=c(2,2))

plot(subset$DateTime, subset$Global_active_power,
     type="l",
     xlab="",
     ylab="Global Active Power")

plot(subset$DateTime, subset$Voltage,
     type="l",
     xlab="datetime",
     ylab="Voltage")

plot(subset$DateTime, subset$Sub_metering_1,
     type="l",
     xlab="",
     ylab="Energy sub metering")
lines(subset$DateTime, subset$Sub_metering_2, col="red")
lines(subset$DateTime, subset$Sub_metering_3, col="blue")
legend("topright",
       col=c("black","red","blue"),
       lty=1,
       bty="n",
       legend=c("Sub_metering_1","Sub_metering_2","Sub_metering_3"))

plot(subset$DateTime, subset$Global_reactive_power,
     type="l",
     xlab="datetime",
     ylab="Global Reactive Power")
dev.off()