plot3.R

file_data <- read.csv('household_power_consumption.txt', sep=';', header=T, na.strings="?")

# cleaning data
data <- subset(file_data, file_data$Date == "2/2/2007" | file_data$Date == "1/2/2007")
data$datetime <- strptime(paste(data$Date, " ", data$Time), format = "%d/%m/%Y %H:%M:%S")
data$Sub_metering_1 <- as.numeric(data$Sub_metering_1)
data$Sub_metering_2 <- as.numeric(data$Sub_metering_2)
data$Sub_metering_3 <- as.numeric(data$Sub_metering_3)

# plot
png(filename = 'plot3.png', width = 480, height = 480)
with(data, plot(datetime, Sub_metering_1, type="n", main="", ylab="Energy sub metering", xlab=""))
with(data, lines(datetime, Sub_metering_1))
with(data, lines(datetime, Sub_metering_2, col = "red"))
with(data, lines(datetime, Sub_metering_3, col = "blue"))
legend("topright", pch = "-", lwd = 1, col = c("black", "red", "blue"), legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))
dev.off()