plot4.R

plot4 <- function() {
    power <- read.csv("household_power_consumption.txt", sep = ";")
    power_target_dates <- power[grep("^[12]/2/2007", power$Date), ]
    datetime <- strptime(paste(power_target_dates$Date, power_target_dates$Time), "%d/%m/%Y %H:%M:%S")
    global_active_power <- as.numeric(as.character(power_target_dates[,"Global_active_power"]))
    voltage <- as.numeric(as.character(power_target_dates[,"Voltage"]))
    sub_metering_1 <- as.numeric(as.character(power_target_dates[,"Sub_metering_1"]))
    sub_metering_2 <- as.numeric(as.character(power_target_dates[,"Sub_metering_2"]))
    sub_metering_3 <- as.numeric(as.character(power_target_dates[,"Sub_metering_3"]))
    global_reactive_power <- as.numeric(as.character(power_target_dates[,"Global_reactive_power"]))
    par(mfrow = c(2, 2))
    # topleft
    plot(datetime, global_active_power, type = "l", xlab = "", ylab = "Global Active Power")
    # top right
    plot(datetime, voltage, type = "l", xlab = "datetime", ylab = "Voltage")
    # bottom left
    plot(datetime, sub_metering_1, type = "l", xlab = "", ylab = "Energy sub metering", col = "black")
    lines(datetime, sub_metering_2, col = "red")
    lines(datetime, sub_metering_3, col = "blue")
    legend("topright", legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), text.col = "black", col = c("black", "red", "blue"), lwd = 1, lty = 1, bty = "n", cex = 0.9)
    # bottom right
    plot(datetime, global_reactive_power, type = "l", xlab = "datetime", ylab = "Global_reactive_power")
}