plot4.R

source("read_data.R") 
png(filename="plot4.png", width=480, height=480)

colors <- c("black", "red", "blue")
par(mfrow=c(2, 2))
with(data, {
		plot(datetime, Global_active_power, type="o", pch=NA, ylab="Global active power", xlab=NA)
		plot(datetime, Voltage, type="o", pch=NA)
		plot(datetime, Sub_metering_1, type="o", pch=NA, ylab="Energy sub metering", xlab=NA)
		points(datetime, Sub_metering_2, type="o", pch=NA, col="red")
		points(datetime, Sub_metering_3, type="o", pch=NA, col="blue")
		legend("topright", legend=c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"), col=colors, text.col=colors, lwd=1, box.lwd=0, inset=.01)
		plot(datetime, Global_reactive_power, type="o", pch=NA)
})

dev.off()