plot3.R

library('lubridate')

setwd("~/R/exdata-034/ExData_Plotting1")
df <- read.csv('./data/household_power_consumption.txt', sep = ";", na.strings = "?")

# Combine date and time fields into POSIXct datetime object
df$datetime <- dmy_hms(paste(df$Date, df$Time))

# subset data from the dates 2007-02-01 and 2007-02-02
data <- df[df$Date == "1/2/2007" | df$Date == "2/2/2007",]

# Plot 3: Energy sum metering over time
png('plot3.png',  width = 480, height = 480)
par(mfrow=c(1,1))
plot(data$datetime, data$Sub_metering_1,
     xlab = "",
     ylab="Energy sub metering",
     type="l")

lines(data$datetime, data$Sub_metering_2,
      col="red")

lines(data$datetime, data$Sub_metering_3,
      col="blue")

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

dev.off()