plot4.R

if (is.null(data)) {
  source("data.R")
}

png("plot4.png", width=480, height=480)

par(mfrow=c(2,2))

plot(data$Time, data$Global_active_power, type="l", xlab="", ylab="Global Active Power")

plot(data$Time, data$Voltage, type="l", xlab="datetime", ylab="Voltage")

plot(data$Time, data$Sub_metering_1, type="l", col="black", xlab="", ylab="Energy sub metering")
lines(data$Time, data$Sub_metering_2, col="red")
lines(data$Time, data$Sub_metering_3, col="blue")
legend("topright", col=c("black", "red", "blue"), c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), lty=1, box.lwd=0)

plot(data$Time, data$Global_reactive_power, type="n", xlab="datetime", ylab="Global_reactive_power")
lines(data$Time, data$Global_reactive_power)

dev.off()