plot1.R

# Read in Data File
df = "household_power_consumption.txt"
hpc<-read.delim(df, header=T, sep=";", na.strings="?")

# Convert date/times into datetime format and select subset of data to work with
hpc$datetime = strptime(paste(hpc$Date,hpc$Time), format="%d/%m/%Y %H:%M:%S")
sd = strptime("01/02/2007 00:00:00", format="%d/%m/%Y %H:%M:%S")
ed = strptime("03/02/2007 00:00:00", format="%d/%m/%Y %H:%M:%S")
twoDays<-subset(hpc, datetime>=sd & datetime<ed, select=3:10)

# View updated stats
summary(twoDays)
str(twoDays)

# Plot #1 - Historgram of Power Usage by kilowatts
png(filename="plot1.png", width=480, height=480)
hist(twoDays$Global_active_power, 
     xlab="Global Active Power (kilowatts)", 
     ylab="Frequency", 
     main="Global Active Power", 
     col="red")
dev.off()