plot3.R

## Set the directory where the repository Electric Power Consumption is. 
## For the purpose of the assignment submission, I remove the directory that I used, 
## if you want to run this code in your own computer, please set your directory first and then run the code. 
directory <- "/" ##Replace here (inside the "") the name of your own directory
setwd(directory)
filename <- "household_power_consumption.txt"
## Extract names of the data set. When I use skip for some reason although I user header=TRUE, they are not retreived.
DataNames <- read.table(filename,sep=";",header=TRUE, nrows=1)
Name_Vector <- names(DataNames)
#Establish a grep to identify which lines to skip and how many lines to extract that correspond with the sub-set of the data. 
start <- grep("1/2/2007", readLines(filename))
end <- grep("3/2/2007", readLines(filename))
DataMatrix <- read.table(filename,sep=";",header=TRUE, skip=start,nrows=end-start-1)
DataMatrix <- setNames(DataMatrix, Name_Vector)
## Transfor Date and time variable to work with them. 
DataMatrix$datetime <- paste(DataMatrix$Date, DataMatrix$Time, sep=" ")
DataMatrix$datetime <- strptime(DataMatrix$datetime, format="%d/%m/%Y %H:%M:%S")
#Transform the numeric variables to a number
DataMatrix$Sub_metering_1 = as.numeric(DataMatrix$Sub_metering_1)
DataMatrix$Sub_metering_2 = as.numeric(DataMatrix$Sub_metering_2)
DataMatrix$Sub_metering_3 = as.numeric(DataMatrix$Sub_metering_3)
#Plot the information
plot(DataMatrix$datetime, DataMatrix$Sub_metering_1, type="l", xlab="", ylab="Energy sub metering", col = "black")
points(DataMatrix$datetime, DataMatrix$Sub_metering_2, type ="l", col = "red")
points(DataMatrix$datetime, DataMatrix$Sub_metering_3, type = "l", col = "blue")
legend("topright", lty=c(1,1,1), col = c("black","red", "blue"), legend = c("Sub_metering_1","Sub_metering_2", "Sub_metering_3"), text.font=2)
#Copy graph to png file. 
dev.copy(png,file ="plot3.png", width = 480, height = 480, units = "px") 
dev.off