plot3.R

#reads the data to dataframe
power_consumption_data <- read.table(file = "household_power_consumption.txt", header = TRUE, sep = ";", na.strings = "?")

#convert date and time columns
power_consumption_data$Date_Time <- with(power_consumption_data, paste(Date, Time))
power_consumption_data$Date_Time <- strptime(power_consumption_data$Date_Time, format = "%d/%m/%Y %T")


selected_date_string <- c("2007-02-01", "2007-02-02")


selected_power_consumption <- subset(power_consumption_data, strftime(Date_Time, format = "%Y-%m-%d") %in% selected_date_string)
selected_power_consumption <- droplevels(selected_power_consumption)


#plot 3

energy_submeting_selection1 <- data.frame(Date_Time = selected_power_consumption$Date_Time, Energy_submetering = selected_power_consumption$Sub_metering_1, Selection = 1)
energy_submeting_selection2 <- data.frame(Date_Time = selected_power_consumption$Date_Time, Energy_submetering = selected_power_consumption$Sub_metering_2, Selection = 2)
energy_submeting_selection3 <- data.frame(Date_Time = selected_power_consumption$Date_Time, Energy_submetering = selected_power_consumption$Sub_metering_3, Selection = 3)
energy_submeting_selection <- rbind(energy_submeting_selection1, energy_submeting_selection2, energy_submeting_selection3)

png(filename = "plot3.png", width = 480, height = 480)
with(energy_submeting_selection, plot(Date_Time, Energy_submetering, type = "n", xlab = "", ylab = "Energy sub metering"))
with(subset(energy_submeting_selection, Selection == 1), lines(Date_Time, Energy_submetering, type = "l", col = "black"))
with(subset(energy_submeting_selection, Selection == 2), lines(Date_Time, Energy_submetering, type = "l", col = "red"))
with(subset(energy_submeting_selection, Selection == 3), lines(Date_Time, Energy_submetering, type = "l", col = "blue"))
legend("topright", col = c("black", "red", "blue"), legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), lty = c(1,1))
dev.off()