plot2.R

## plot2()
##
## Purpose: Look at time-series data, plotting global active power for two days in February
##
## Note: Assumes the dataset has already been unzipped and is sitting in the current working directory

plot2 <- function() {
  ## Read in the data
  data <- read.table("household_power_consumption.txt", header = T, sep = ";", colClasses = c(NA, NA, "numeric", "numeric", "numeric", "numeric", "numeric", "numeric", "numeric"), stringsAsFactors = F, na.strings = "?")
  
  ## Convert dates/times from character
  data$Date <- as.Date(data$Date, format = "%d/%m/%Y")
  data$Time <- strptime(data$Time, format = "%H:%M:%S")
  
  ## Restrict the dates to the first two days in February 2007
  data <- data[(data$Date > "2007-01-31" & data$Date < "2007-02-03"), ]
  
  ## Generate our correct date-time variable
  data$DateTime <- as.POSIXlt(paste(data$Date, format(data$Time, format = "%H:%M:%S")))
  
  
  
  ## Plot the Global Active Power data as a time series; generate PNG
  png(filename = "plot2.png")
  plot(data$DateTime, data$Global_active_power, type = "n", xlab = "", ylab = "Global Active Power (kilowatts)")
  lines(data$DateTime, data$Global_active_power)
  dev.off()
}