plot3.R

## Set working directory
setwd("/media/removable/SD Card/Research/Analysis/Coursera/Exploratory Data Analysis/Course Project 01")

## Load data
powerText = readLines("household_power_consumption.txt")
powerTextSubset = grep("^[12]/2/2007", substr(powerText, 1, 8))
power = read.table(text=powerText[powerTextSubset], header=TRUE, sep=";",
                   na.strings="?", col.names=c("Date", "Time",
                                               "Global_active_power",
                                               "Global_reactive_power",
                                               "Voltage", "Global_intensity",
                                               "Sub_metering_1",
                                               "Sub_metering_2",
                                               "Sub_metering_3"))

rm(powerText, powerTextSubset)

# Convert date & time format
power$Date_time = strptime(paste(power$Date, power$Time, sep=" "),
                           format="%d/%m/%Y %H:%M:%S")

## View plot
# windows()  # Windows
# quartz()  # Mac
x11()  # Linux
plot(power$Date_time, power$Sub_metering_1, type="l", xlab="", xaxt="n",
     ylab="Energy sub metering")
lines(power$Date_time, power$Sub_metering_1, col="black")
lines(power$Date_time, power$Sub_metering_2, col="red")
lines(power$Date_time, power$Sub_metering_3, col="blue")
axis.POSIXct(1, power$Date_time, format="%a", labels = TRUE)
legend("topright", col = c("black", "red", "blue"), lwd=1, legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))

## Export plot
png(filename="plot3.png", width=480, height=480)
plot(power$Date_time, power$Sub_metering_1, type="l", xlab="", xaxt="n",
     ylab="Energy sub metering")
lines(power$Date_time, power$Sub_metering_1, col="black")
lines(power$Date_time, power$Sub_metering_2, col="red")
lines(power$Date_time, power$Sub_metering_3, col="blue")
axis.POSIXct(1, power$Date_time, format="%a", labels = TRUE)
legend("topright", col = c("black", "red", "blue"), lwd=1, legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))
dev.off()