plot3.R

## DEPENDENCIES: sqldf
## EFF: read household_power_consumption.txt from current dir,
##      create time plot of 3 energy sub-meterings, and
##      output it as plot3.png

library(sqldf)
Sys.setlocale(category = "LC_TIME", locale = "C")
household <- read.csv2.sql("household_power_consumption.txt",
        "SELECT * FROM file WHERE Date = '1/2/2007' OR Date = '2/2/2007'",
        na.strings = "?")
date_time <- paste(household$Date, household$Time, sep = "/")
date_time <- strptime(date_time, "%d/%m/%Y/%H:%M:%S")
household$Date_time <- date_time

par(yaxp = c(0, 40, 3))
with(household, plot(Date_time, Sub_metering_1, type = "l", 
	xlab = "", ylab = "Energy sub metering"))
lines(household$Date_time, household$Sub_metering_2, col = "red")
lines(household$Date_time, household$Sub_metering_3, col = "blue")
legend("topright", pch = NA, lwd = 1, col = c("black", "red", "blue"), 
	legend = c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3")) 

dev.copy(png, "plot3.png")
dev.off()