plot4.R

source("load_data.R")

quad_plot <- function() {
  
  par(mfrow=c(2, 2))
  
  # 1st quadrant, global active power
  with(power2, plot(DateTime, Global_active_power, type="l", 
                    ylab="Global Active Power (kilowatts)",
                    xlab="")) 
    
  # 2nd quadrant, voltage
  with(power2, plot(DateTime, Voltage, type="l")) 

  # 3rd quadrant, sub meterings
  plot(power2$DateTime, power2$Sub_metering_1, type="l", col="Black",
       ylab="Global Active Power (kilowatts)",
       xlab="", ylim=c(0, 30))
  
  lines(power2$DateTime, power2$Sub_metering_2,col="Red")
  lines(power2$DateTime, power2$Sub_metering_3,col="Blue")
  legend("topright", 
         legend=c("Sub_metering_1", 
                  "Sub_metering_2",
                  "Sub_metering_3"), 
         lty=1,
         bty="n",
         col=c("Black",              
               "Red",
               "Blue"))
    
  # 4th quadrant, global reactive power
  with(power2, plot(DateTime, Global_reactive_power, type="l"))
}

quartz()
par(mar=c(5.0, 4.0, 2.0, 1.5))
quad_plot()
dev.copy(png, file="plot4.png")
dev.off()