Power Consumption Exploratory Analysis

Executive Summary

Exploratory analysis of “Individual household electric power consumption” Data Set from University of California Machine Learning Repository to examine household energy usage over a 2-day period in February 2007.

Data Processing

#Download File
if(!file.exists("exdata-data-household_power_consumption.zip")) {
    temp <- tempfile()
    download.file("http://d396qusza40orc.cloudfront.net/exdata%2Fdata%2Fhousehold_power_consumption.zip",temp)
    file <- unzip(temp)
    unlink(temp)
}

#Read table
power <- read.table(file, header=T, sep=";")

#Format dates
power$Date <- as.Date(power$Date, format="%d/%m/%Y")

#Subset data for 2/1/2007 and 2/2/2007
df <- power[(power$Date=="2007-02-01") | (power$Date=="2007-02-02"),]
df$Global_active_power <- as.numeric(as.character(df$Global_active_power))
df$Global_reactive_power <- as.numeric(as.character(df$Global_reactive_power))
df$Voltage <- as.numeric(as.character(df$Voltage))
df <- transform(df, timestamp=as.POSIXct(paste(Date, Time)), "%d/%m/%Y %H:%M:%S")
df$Sub_metering_1 <- as.numeric(as.character(df$Sub_metering_1))
df$Sub_metering_2 <- as.numeric(as.character(df$Sub_metering_2))
df$Sub_metering_3 <- as.numeric(as.character(df$Sub_metering_3))

Exploratory Analysis

Exploratory Plot 1

plot1 <- function() {
    hist(df$Global_active_power, main = paste("Global Active Power"), col="gold", xlab="Global Active Power (kilowatts)")
    dev.copy(png, file="ucplot1.png", width=480, height=480)
    dev.off()
}
plot1()

png 
  2 

Exploratory Plot 2

plot2 <- function() {
    plot(df$timestamp,df$Global_active_power, type="l", xlab="", ylab="Global Active Power (kilowatts)")
    dev.copy(png, file="ucplot2.png", width=480, height=480)
    dev.off()
}
plot2()

png 
  2 

Exploratory Plot 3

plot3 <- function() {
    plot(df$timestamp,df$Sub_metering_1, type="l", xlab="", ylab="Energy sub metering")
    lines(df$timestamp,df$Sub_metering_2,col="red")
    lines(df$timestamp,df$Sub_metering_3,col="blue")
    legend("topright", col=c("black","red","blue"), c("Sub_metering_1  ","Sub_metering_2  ", "Sub_metering_3  "),lty=c(1,1), lwd=c(1,1))
    dev.copy(png, file="ucplot3.png", width=480, height=480)
    dev.off()
}
plot3()

png 
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Exploratory Plot 4

plot4 <- function() {
    par(mfrow=c(2,2))
    
    #Plot 1
    plot(df$timestamp,df$Global_active_power, type="l", xlab="", ylab="Global Active Power")
    
    #Plot 2
    plot(df$timestamp,df$Voltage, type="l", xlab="datetime", ylab="Voltage")
    
    #Plot 3
    plot(df$timestamp,df$Sub_metering_1, type="l", xlab="", ylab="Energy sub metering")
    lines(df$timestamp,df$Sub_metering_2,col="red")
    lines(df$timestamp,df$Sub_metering_3,col="blue")
    legend("topright", col=c("black","red","blue"), 
           c("Sub_metering_1  ","Sub_metering_2  ", "Sub_metering_3  "),lty=c(1,1), bty="n", cex=.5) 
    #bty removes the box, cex shrinks the text, spacing added after labels so it renders correctly
    
    #Plot 4
    plot(df$timestamp,df$Global_reactive_power, type="l", xlab="datetime", ylab="Global_reactive_power")
    
    #Output
    dev.copy(png, file="ucplot4.png", width=480, height=480)
    dev.off()
}
plot4()

png 
  2