plot4.R

data <- read.csv("household_power_consumption.txt", header=TRUE, sep=';', na.strings="?")

data$Date <- as.Date(data$Date, format="%d/%m/%Y")

data <- subset(data, Date >= "2007-02-01" & Date <= "2007-02-02")

datetime <- paste(as.Date(data$Date), data$Time)

data$Datetime <- as.POSIXct(datetime)

par(mfrow=c(2,2), mar=c(4,4,2,1), oma=c(0,0,2,0))
with(data, {
  plot(Global_active_power~Datetime, type="l", 
       ylab="Global Active Power", xlab="")
  plot(Voltage~Datetime, type="l", 
       ylab="Voltage", xlab="datetime")
  plot(Sub_metering_1~Datetime, type="l", 
       ylab="Energy sub metering", 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, bty="n",
         legend=c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))
  plot(Global_reactive_power~Datetime, type="l", 
       ylab="Global_reactive_power",xlab="datetime")
})

dev.copy(png, file="plot4.png", height=480, width=480)

dev.off()