plot2.R

#This function requires the lubridate and plyr packages
plot2 <- function(){
    #load required libraries
    library(lubridate)
    library(plyr)
    #open the file (we found out from previous analysis thSysat the rows with the required data are the ones between 66637 and 69516 , both included)
    #here's the filter code, for reference, even if we don't need it anymore
    #electric<- electric[electric$Date >= dmy("01-02-2007") & electric$Date <=dmy("02-02-2007"),]
    
    #read first line only to use as headers, then skip the uninteresting data to save memory
    headers <- read.table("household_power_consumption.txt", na.strings="?", sep=";",header=FALSE, nrow=1)
    electric <- read.table("household_power_consumption.txt", na.strings="?", sep=";", 
                           header=FALSE, skip = 66637, nrow=2880)
    colnames(electric)<-unlist(headers)
    #mutate the Date and Time columns into proper date and time objects
    electric <- mutate(electric, Date = dmy(Date))
    electric <- mutate(electric, Time = hms(Time))
    
    #The code up to this part could be saved in a different file for reutilization
    #on different plots, but since it is an assigment, we'll copy it for clarity. 
    
    electric <- mutate(electric, DateTime = Date+Time)
    
    #if you don't have English as your native language, remember to set the locale!
    #Sys.setlocale("LC_TIME", "English")
    png("plot2.png",480,480)
    with(electric, plot(DateTime,Global_active_power, type="l", xlab = "", ylab="Global Active Power (kilowatts)"))
    dev.off()
}