plot2.R

#################################################################################
# Library Load Section.
# Library being used : lubridate
#################################################################################
require(lubridate)


#################################################################################
# Data Reading Section.
# This section is to read raw data of household power consumption.
# Data will be used is only from the dates 2007-02-01 and 2007-02-02.
#################################################################################

#Read the data from text file then subset only from the dates 
#2007-02-01 and 2007-02-02
dataset <- read.table(file = "household_power_consumption.txt", 
                      sep = ";", 
                      header = TRUE, 
                      na.strings = "?" , 
                      stringsAsFactors = FALSE)

dataset <- subset(dataset, 
                  dataset$Date == "1/2/2007" | dataset$Date == "2/2/2007")


#Create a new DateTime column from combination of Date & Time column 
#in dataset
datetime <- strptime(paste(dataset$Date,dataset$Time), "%d/%m/%Y %H:%M:%S")
dataset <- cbind(datetime, dataset)
names(dataset)[1] <- "DateTime"

#Parse Date and Time string into correspondingg Data and Time class
dataset$Date <- dmy(dataset$Date)
dataset$Time <- hms(dataset$Time)

#Remove unnecesary temporary variable
rm(datetime)


#################################################################################
# Data Plotting Section.
# This section is to create a data plot and send the output to PNG file device
#################################################################################
png(file = "plot2.png")

with(dataset, 
     plot(DateTime, 
          Global_active_power, 
          type = "l", 
          xlab = "",
          ylab = "Global Active Power (kilowatts)"
          )
     )

dev.off()