plot3.R

library(dplyr)
Household <- read.csv(file = "C:/Users/johns/Documents/R/household_power_consumption.txt", header = TRUE, sep = ";", na.strings = "?", nrows=2075259, check.names = F, stringsAsFactors = F, comment.char = "")
subset_household <- subset(Household, Date %in% c("1/2/2007","2/2/2007"))
subset_household$Date <- as.Date(subset_household$Date, format="%d/%m/%Y")
datetime <- paste(as.Date(subset_household$Date), subset_household$Time)
subset_household$Datetime <- as.POSIXct(datetime)

with(subset_household, {plot(Sub_metering_1~Datetime, type="l", ylab="Global Active Power(kilowatts)", xlab="")
    lines(Sub_metering_2~Datetime, col="red")
    lines(Sub_metering_3~Datetime, col="blue")
    })
legend("topright", col=c("black", "red", "blue"), lty=1, lwd=2, legend=c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))

dev.copy(png, file="plot3.png", height=480, width=480)
dev.off()