Plot3.R

##read txt file in which columns are separated by ; and missing values are labeled with ?

power <- read.table("household_power_consumption.txt", header = TRUE, sep = ";", na.strings = "?")

## first column is Date and this command formats integers into date format
power[[1]] <- as.Date(strptime(power[[1]],format = "%d/%m/%Y"))

## this command subset for specific dates 
powers <- subset(power, Date >= "2007-02-01" & Date <"2007-02-03")
powers$datetime <- as.POSIXct(paste(powers$Date, powers$Time), format="%Y-%m-%d %H:%M:%S")
#saving png file of Frequency plot
png(filename = "Plot3.png")

with (powers, plot(datetime, Sub_metering_1, type="n", ylab="Energy sub metering", xlab=" "))
lines(powers$datetime, powers$Sub_metering_1)
lines(powers$datetime, powers$Sub_metering_2, col="red")
lines(powers$datetime, powers$Sub_metering_3, col="blue")
##legend insert
legend("topright", legend = c("Sub_metering_1", "Sub_metering_2","Sub_metering_3"), lty = 1, col = c("black","red","blue"))
dev.off()