plot4.R

skip <- 66637
end <- 69517

filename <- "household_power_consumption.txt"
mycolnames <- c("Date","Time","Global_active_power","Global_reactive_power","Voltage","Global_intensity","Sub_metering_1","Sub_metering_2","Sub_metering_3")
df <- read.table(filename, sep = ";", na.strings = "?", skip = skip, nrows = end-skip)
colnames(df) <- mycolnames

png(file = "plot4.png")
DateTime <- paste(df$Date, df$Time)
DateTime <- as.POSIXct(DateTime, format = "%d/%m/%Y %H:%M:%S")
df$DateTime <- DateTime


par(mfrow=c(2,2))

# Plot 1
plot(df$DateTime, df$Global_active_power, type="l",
     xlab = "", ylab = "Global Active Power")

# Plot 2
plot(df$DateTime, df$Voltage, type="l",
     xlab = "datetime", ylab = "Voltage")

# Plot 3
plot(df$DateTime, df$Sub_metering_1, type="l", col = "black",
     xlab = "", ylab = "Energy sub metering")
points(df$DateTime, df$Sub_metering_2, type="l", col = "red")
points(df$DateTime, df$Sub_metering_3, type="l", col = "blue")
legend("topright", col = c("black","red","blue"), lty=c(1,1), bty = "n",
       legend = c("Sub_metering_1","Sub_metering_2","Sub_metering_3"))

# Plot 4
plot(df$DateTime, df$Global_reactive_power, type="l",
     xlab = "datetime", ylab = "Global_reactive_power")

dev.off()