plot4.R

## Read data. Data file name is household_power_consumption.txt
data.raw <- read.csv("household_power_consumption.txt", na.strings = "?", 
                      sep = ";", stringsAsFactors = FALSE)
data <- data.raw[data.raw$Date == "1/2/2007" | data.raw$Date == "2/2/2007", ]

## Plot
png(filename = "plot4.png", width = 480, height = 480)
x <- seq(as.POSIXct("2007-02-01 00:00:00"), by="mins", length.out=24*60*2)
par(mfrow = c(2,2))

with(data, {
        
        #Plot topleft
        plot(x, Global_active_power, ylab = "Global Active Power", 
             xlab = "", type = "l")
        
        #Plot topright
        plot(x, Voltage, ylab = "Voltage", 
             xlab = "datetime", type = "l")
        
        #Plot bottomleft
        plot(x, Sub_metering_1, ylab = "Energy sub metering", 
             xlab = "", type = "l")
        lines(x, Sub_metering_2, col = "red")
        lines(x, Sub_metering_3, col = "blue")
        legend("topright", col = c("black", "red", "blue"), 
               legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), 
               bty = "n", lty = 1)
        
        #Plot bottomright
        plot(x, Global_reactive_power, xlab = "datetime", type = "l")
})
dev.off()