plot3.R

power <- read.csv( "household_power_consumption.txt", sep = ";", na.strings = c("?") )

# head(power)
#        Date     Time Global_active_power Global_reactive_power Voltage
# 1 16/12/2006 17:24:00               4.216                 0.418  234.84
#  Global_intensity Sub_metering_1 Sub_metering_2 Sub_metering_3
# 1             18.4              0              1             17

# "We will only be using data from the dates 2007-02-01 and 2007-02-02."

# "Add the PNG file and R code file to your git repository"

# "Construct the plot and save it to a PNG file with a width of 480 pixels and a height of 480 pixels."
# this seems to be the default.

power$timestamp = as.POSIXct(paste0(power$Date, " ", power$Time), format="%d/%m/%Y %H:%M:%S")

power <- power[  power$timestamp >= as.POSIXct("2007-02-01") & power$timestamp < as.POSIXct("2007-02-03"), ] 

png(file = "plot3.png", width = 480, height = 480, units = "px") 

plot( power$timestamp, power$Sub_metering_1, ylab = "Energy sub metering", xlab="", type="l" )  
lines( power$timestamp, power$Sub_metering_2, col="red" )
lines( power$timestamp, power$Sub_metering_3, col="blue" )

legend("topright", col = c("black", "red", "blue"), legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), lty=1, lwd=1 )

dev.off()