plot2.R

## Exploratory Data Analysis Project 1
## Global active power in time
## plot2.R -------> plot2.png

## Load data file and convert Date and time objects
powerdata<- read.csv("household_power_consumption.txt", sep=";", 
                     colClasses = c("character", "character","numeric","numeric","numeric",
                                    "numeric","numeric","numeric","numeric"),
                     na.strings = "?")                                             
powerdata$Time <- strptime(paste(powerdata$Date, powerdata$Time), "%d/%m/%Y %H:%M:%S")## keep #Var at 9
powerdata$Date <- as.Date(powerdata$Date, "%d/%m/%Y")
## Create a data subset for the require time frame
Dates <- as.Date(c("2007-02-01", "2007-02-02"), "%Y-%m-%d")
pdata_subset <- subset(powerdata, Date %in% Dates)
## Date  and Time and change date format
pdata_subset$Datetime <- as.POSIXct(pdata_subset$Time) ## subset aditional var for clarity
## Save plot in png format
png("plot2.png" , width = 480, height = 480) ## notice that dates are in french
## Create plot Global Active Power vs Time

plot(pdata_subset$Datetime, pdata_subset$Global_active_power, type="l",
     ylab="Global Active Power (kilowatts)", xlab="")

dev.off()