plot4.R

# read data
data_ <- read.table("household_power_consumption.txt", sep = ";", na.strings = "?", header = T);
# Convert date and time
data_$Time <- strptime(x = paste(data_$Date, data_$Time, sep = " "), format = "%d/%m/%Y %H:%M:%S")
data_$Date <- as.Date(data_$Date,format = '%d/%m/%Y')

start_ <- as.Date("2007-02-01")
end_ <- as.Date("2007-02-02")

data2 <- data_[which(data_$Date >= start_ & data_$Date <= end_),]

# draw plot 4
png(file = "plot4.png", width = 480, height = 480, units = "px")

par(mfrow=c(2,2))
# 1
plot(
  x = data2$Time,
  y = data2$Global_active_power,
  type = "l",
  xlab="",
  ylab="Global Active Power"
)

# 2
plot(
  x = data2$Time,
  y = data2$Voltage,
  type = "l",
  xlab="datetime",
  ylab="Voltage"
)

# 3
plot(
  x = data2$Time,
  y = data2$Sub_metering_1,
  type = "l",
  xlab="",
  ylab="Energy sub metering"
)

lines(
  x=data2$Time,
  y=data2$Sub_metering_2,
  col="red")

lines(
  x=data2$Time,
  y=data2$Sub_metering_3,
  col="blue")

legend("topright",c("Sub_metering_1","Sub_metering_2","Sub_metering_3"),bty="l",col=c("black","red","blue"),lwd=2,cex=0.7)

# 4
plot(
  x = data2$Time,
  y = data2$Global_reactive_power,
  type = "l",
  xlab="datetime",
  ylab="Global_reactive_power"
)

dev.off()