plot3.R

#The first four commands should only be run if the data is not already unzipped into your working directory
temp <- tempfile()
download.file("http://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip",temp)
power <- read.table(unz(temp, "household_power_consumption.txt"),sep=";", header=T, stringsAsFactors=F)
unlink(temp)

#Read the unzipped data file from working directory
power <- read.table("household_power_consumption.txt", header = T, sep = ";", stringsAsFactors=F, na.strings=c("?"))
#Subset the data to just the first two days in February 2007, date is in %d%m%Y format
dateSubset<- power[power$Date %in% c("1/2/2007","2/2/2007") ,]
#Paste the Date and Time variables together in Date/Time format
dateSubset$DateTime <- strptime(paste(dateSubset$Date, dateSubset$Time), "%d/%m/%Y %H:%M:%S")
#Open a png graphics device
png(filename="plot3.png", width=480, height=480)
#Create an empty plot with the max range taken from Sub_metering_1 variable
par(mfrow=c(1,1))
plot(dateSubset$DateTime, dateSubset$Sub_metering_1, type = "n", ylab = "Energy sub metering", xlab = "") 
#Now fill in the plot
lines(dateSubset$DateTime, dateSubset$Sub_metering_1, col="black")
lines(dateSubset$DateTime, dateSubset$Sub_metering_2, col= "red")
lines(dateSubset$DateTime, dateSubset$Sub_metering_3, col= "blue")
#Create a legend
legend("topright", legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), lty = c(1,1), col = c("black","red", "blue")) 
#Close graphic device
dev.off()