plot2.R

# Read data
firstRow <- 66638  # First row with a 1/2/2007 date

data <- read.table('household_power_consumption.txt', sep = ";", skip = firstRow - 1, nrows = 60*24*2, stringsAsFactors = FALSE)

# Read column names
strnames <- readLines('household_power_consumption.txt', n = 1)

# Assign column names
splitnames <- strsplit(strnames, ";")
names(data) <- splitnames[[1]]

# Convert date and time variables to date/time classes

data$datetime <- strptime(paste(data$Date, data$Time), "%d/%m/%Y %H:%M:%S")
data$Date <- NULL
data$Time <- NULL

# Make plot 2

png(filename = "plot2.png", width = 480, height = 480)
with(data, plot(datetime, Global_active_power, type = "l", 
	xlab = "", ylab = "Global Active Power (kilowatts)"))
dev.off()