plot1.R

data <- read.table('household_power_consumption.txt', sep=';', header=T, 
                   colClasses = c('character', 'character', 'numeric',
                                  'numeric', 'numeric', 'numeric',
                                  'numeric', 'numeric', 'numeric'),
                   na.strings='?')

# strip the data time
data$DateTime <- strptime(paste(data$Date, data$Time), 
                          "%d/%m/%Y %H:%M:%S")
# set the data time for the days 1 & 2 of month 02 
data <- subset(data, as.Date(DateTime) >= as.Date("2007-02-01") & 
                 as.Date(DateTime) <= as.Date("2007-02-02"))

# open a '.png' file
png("plot1.png", height=500, width=500)

hist(data$Global_active_power, col='red', 
     xlab = 'Global Active Power (kilowatts)',
     main = 'Global Active Power')

# close
dev.off()