plot4.R

    #Download the data
    filename <- "Coursera_EDA_Assignment1.zip"
    
    # Checking if archieve already exists.
    if (!file.exists(filename)){
        fileURL <- "https://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip"
        download.file(fileURL, filename, method="curl")
    }  
    
    # Checking if the unzipped folder exists and unzip if it doesn't
    if (!file.exists("household_power_consumption.txt")) { 
        unzip(filename) 
    } else { 
        print("File exists")
    }
    
    # Import the dataset:
    library(readr)
    
    household_power_consumption <- read_delim("household_power_consumption.txt", 
                                              ";", escape_double = FALSE, 
                                              col_types = cols(Date = col_date(format = "%d/%m/%Y")),
                                              trim_ws = TRUE)
    
    # Subset between dates
    df <- household_power_consumption[
        which(household_power_consumption$Date>="2007-02-01" & 
                  household_power_consumption$Date<="2007-02-02"),
        ]
    
    # Create the dateTime variable
    df$dateTime <- as.POSIXct(paste(df$Date, df$Time), format="%Y-%m-%d %H:%M:%S")
    
    with(df,{
        # Prepare png device:
        png(filename="plot4.png", 
            width=480, 
            height=480)
        
        # Set parameters for multiple plots
        par(mfrow=c(2,2))
        
        # Create the plots
        # First plot
        plot(dateTime, Global_active_power, type="l", lwd=1, col="black", 
             ylab="Global Active Power", xlab = "")
        
        # Create the second plot
        plot(dateTime, Voltage, type="l", lwd=1, col="black", 
             ylab="Voltage")       
        
        # Create third plot
        plot(dateTime, Sub_metering_1, type="l", lwd=1, col="black", 
             ylab="Energy sub metering", xlab = "") 
           
            # Add in additional variables:
            lines(dateTime,Sub_metering_2, lwd=1, col="red") 
            lines(dateTime,Sub_metering_3, lwd=1, col="blue")     
        
            # Add the legend without a boarder:
            legend("topright", 
                   legend=c("Sub_metering_1","Sub_metering_2","Sub_metering_3"), 
                   lwd=c(2,2), 
                   col=c("black", "red", "blue"),
                   bty = "n") 
        
        # Create the fourth plot
        plot(Global_reactive_power~dateTime, type="l", 
             xlab="dateTime",
             ylab="Global_reactive_power")
        
        dev.off()
    }      
    )