ExData_Plotting1: An R repository from alexgallax

Introduction

This assignment uses data from the UC Irvine Machine Learning Repository, a popular repository for machine learning datasets. In particular, we will be using the "Individual household electric power consumption Data Set" which I have made available on the course web site:

Dataset: Electric power consumption [20Mb]
Description: Measurements of electric power consumption in one household with a one-minute sampling rate over a period of almost 4 years. Different electrical quantities and some sub-metering values are available.

The following descriptions of the 9 variables in the dataset are taken from the UCI web site:

Date: Date in format dd/mm/yyyy
Time: time in format hh:mm:ss
Global_active_power: household global minute-averaged active power (in kilowatt)
Global_reactive_power: household global minute-averaged reactive power (in kilowatt)
Voltage: minute-averaged voltage (in volt)
Global_intensity: household global minute-averaged current intensity (in ampere)
Sub_metering_1: energy sub-metering No. 1 (in watt-hour of active energy). It corresponds to the kitchen, containing mainly a dishwasher, an oven and a microwave (hot plates are not electric but gas powered).
Sub_metering_2: energy sub-metering No. 2 (in watt-hour of active energy). It corresponds to the laundry room, containing a washing-machine, a tumble-drier, a refrigerator and a light.
Sub_metering_3: energy sub-metering No. 3 (in watt-hour of active energy). It corresponds to an electric water-heater and an air-conditioner.

Loading the data

To reproduce plots making dataset file must be located in R working directory. It can be downloaded by the link.
The raw dataset in file has 2,075,259 rows and 9 columns.
We only use data from the dates 2007-02-01 and 2007-02-02. So the scripts read the data from just those dates.
The Date and Time variables are converted to Date/Time classes in R using the strptime() and as.Date() functions.
Dataset missing values are coded as ?.

Making Plots

Our overall goal here is simply to examine how household energy usage varies over a 2-day period in February, 2007. The task is to reconstruct the example plots in figue folder, all of which were constructed using the base plotting system.

Examples were forked from the following GitHub repository: https://github.com/rdpeng/ExData_Plotting1

For each plot:

Constructed the plot and saved to a PNG file with a width of 480 pixels and a height of 480 pixels.
Each of the plot files is named as plot1.png, plot2.png, etc.
Created a separate R code file (plot1.R, plot2.R, etc.) that constructs the corresponding plot, i.e. code in plot1.R constructs the plot1.png plot. Code file includes code for reading the data so the plot can be fully reproduced. Also the code that creates the PNG file is included.
The PNG file and R code file added to git repository.