plot1.R

plot1 <- function () {
    # load the data for 1-2 Feb 2007
    pc1 <- loadPCdays()  
    
    #  png (filename ='plot1.png', bg ='transparent', width=504, height=504)
    
    # create the plot on a transparant background (is in the example provided)
    par (bg='transparent', cex=0.75, omi=c(0, 0.05, 0, 0))
    hist(pc1$Global_active_power, col='red', main='Global Active Power',
         xlab='Global Active Power (kilowatts)')
    
    # copy to the png file with the same size as the example provided
    dev.copy(png, file = "plot1.png")
    dev.off()
}

loadPCdays <- function () {
    pc0 <<- read.csv('household_power_consumption.txt', sep=';', na.strings='?')
    # select the rows for Feb 1-2, 2007
    pc1 <- pc0[(pc0$Date=='1/2/2007')|(pc0$Date=='2/2/2007'),]
    #add DateTime column
    pc1$DateTime = strptime(paste (pc1$Date,pc1$Time, sep=' '), "%d/%m/%Y %H:%M:%S", tz='')
    pc1
}