plot4.R

source("load_data.R")

plot4 <- function(data=NULL) {
    if(is.null(data))
        data <- loaddata()

    png("plot4.png", width=504, height=504)
    par(mfrow=c(2,2))
    # plot diagram1 
    plot(data$Time, data$Global_active_power,
         type="l",
         xlab="",
         ylab="Global Active Power")
    # plot diagram2
    plot(data$Time, data$Voltage, type="l",
         xlab="datetime", ylab="Voltage")
    # plot diagram3
    plot(data$Time, data$Sub_metering_1, type="l", col="black",
         xlab="", ylab="Energy sub metering")
    lines(data$Time, data$Sub_metering_2, col="red")
    lines(data$Time, data$Sub_metering_3, col="blue")
    legend("topright",
           col=c("black", "red", "blue"),
           c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"),
           lty=1, bty="n",
           box.lwd=0)
    # plot diagram4
    plot(data$Time, data$Global_reactive_power, type="l",
         xlab="datetime", ylab="Global_reactive_power")
    lines(data$Time, data$Global_reactive_power)
    
    dev.off()

}