plot4.R

### 
# This script uses data from http://archive.ics.uci.edu/ml/
# The specifci data set is : https://archive.ics.uci.edu/ml/datasets/Individual+household+electric+power+consumption#
#
# This script assumes the dataset 
# (https://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip) 
# is already downloaded and unzipped in the working directory
# (to prevent performance or networking issues)
#
# Note after unzipping the data is found in the file household_power_consumption.txt
#

# Goal   : Create 4 graphs over a 2 day period in 2007
# 
# Format : PNG
# Size   : 480 pixels x 480 pixels

# Note: While plotting to the screen the legend overwrites the whole plot, when the smae plot is used for png it looks correct.

# Read set from current working directory



# Make sure we read the date as a class Date
setClass("text2Date")
setAs("character","text2Date", function(from) as.Date(from, format="%d/%m/%Y") )

# Read all data <TODO filter while reading>
HoHoPowerCons <- read.csv("household_power_consumption.txt", header=TRUE, sep=";", stringsAsFactors = FALSE, na.strings = "?", colClasses = c("myDate", "character", rep("numeric", 7)))

# get subset for plots only interested in  2007-02-01 and 2007-02-02
# could do this in one line with the plot command...
plotperiod <- HoHoPowerCons[which(HoHoPowerCons$Date >= "2007-02-01" & HoHoPowerCons$Date <= "2007-02-02"),]


png("plot4.png")

# First set up the 2 x 2 plots.
par(mfrow = c(2, 2))

# First plot upper left
plot(plotperiod$Global_active_power, xlab="", xaxt = "n", ylab="Global Active Power", type="n")
# Add modified x axis <TODO Check if there is a better way>
axis(1, at=c(0, 1440, 2880), labels = c("Thu", "Fri", "Sat"))
lines(plotperiod$Global_active_power)

# second plot upper right
plot(plotperiod$Voltage, xlab="datetime", xaxt = "n", ylab="Voltage", type="n")
# Add modified x axis <TODO Check if there is a better way>
axis(1, at=c(0,1440,2880), labels = c("Thu", "Fri", "Sat"))
lines(plotperiod$Voltage)

# Third plot, lower left
plot(plotperiod$Sub_metering_1, xlab="", xaxt = "n", ylab="Energy sub metering", type="n")
# Add modified x axis <TODO Check if there is a better way>
axis(1, at=c(0,1440,2880), labels = c("Thu", "Fri", "Sat"))
lines(plotperiod$Sub_metering_1, col="black")
lines(plotperiod$Sub_metering_2, col="red")
lines(plotperiod$Sub_metering_3, col="blue")
legend(x="topright", lty=1, col=c("black", "red", "blue"), legend=c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3"))

# Fourth plot, lower right
plot(plotperiod$Global_reactive_power, xlab="datetime", xaxt = "n", ylab="Global_reactive_power", type="n")
# Add modified x axis <TODO Check if there is a better way>
axis(1, at=c(0,1440,2880), labels = c("Thu", "Fri", "Sat"))
lines(plotperiod$Global_reactive_power)

dev.off()