plot4.R

## Getting whole dataset 
data_all <- read.csv("./data/household_power_consumption.txt", header=T, sep=';', na.strings="?", nrows=2075259, check.names=F, stringsAsFactors=F, comment.char="", quote='\"') 
data_all$Date <- as.Date(data_all$Date, format="%d/%m/%Y") 

## Subsetting the data 
data <- subset(data_all, subset=(Date >= "2007-02-01" & Date <= "2007-02-02")) 
rm(data_all) 

## Converting dates 
datetime <- paste(as.Date(data$Date), data$Time) 
data$Datetime <- as.POSIXct(datetime) 

## Creating Plot 4 
par(mfrow=c(2,2), mar=c(4,4,2,1), oma=c(0,0,2,0)) 
with(data, { 
  plot(Global_active_power~Datetime, type="l",  
       ylab="Global Active Power (kilowatts)", xlab="") 
  plot(Voltage~Datetime, type="l",  
       ylab="Voltage (volt)", xlab="") 
  plot(Sub_metering_1~Datetime, type="l",  
       ylab="Global Active Power (kilowatts)", xlab="") 
  lines(Sub_metering_2~Datetime,col='Red') 
  lines(Sub_metering_3~Datetime,col='Blue') 
  legend("topright", col=c("black", "red", "blue"), lty=1, lwd=2, bty="n", 
         legend=c("Sub_metering_1", "Sub_metering_2", "Sub_metering_3")) 
  plot(Global_reactive_power~Datetime, type="l",  
       ylab="Global Rective Power (kilowatts)",xlab="") 
}) 


## Saving to png file 
dev.copy(png, file="plot4.png", height=480, width=480) 
dev.off()