plot2.R

## Plot 2

# setwd("~/Work/Ds/ExploratoryDataAnalysis") # dir where R can find "household_power_consumption.txt"

## Load data

Data = read.csv2(file="household_power_consumption.txt", dec=".", na.strings="?", colClasses=c(rep("character", 2), rep("numeric", 7)))
DateTime = paste(Data$Date, Data$Time)
Data$DateTime = strptime(DateTime, "%d/%m/%Y %H:%M:%S") # convert to POSIXlt
Data$Date = as.Date(Data$Date, "%d/%m/%Y")

SelDate = Data$Date >= "2007-02-01" & Data$Date <= "2007-02-02"

Data2 = Data[SelDate,]
rm(Data)

## Plot

IdxThu = min(which(Data2$Date == "2007-02-01"))
IdxFri = min(which(Data2$Date == "2007-02-02"))
IdxSat = max(which(Data2$Date == "2007-02-02")) + 1
IdxLabel = c(IdxThu, IdxFri, IdxSat)
Label = c("Thu", "Fri", "Sat")

png("plot2.png", height=480, width=480)
with(Data2, {
     plot(Global_active_power, xlab="", ylab="Global Active Power (kilowatts)", type="l", xaxt="n");
     axis(1, at=IdxLabel, labels=Label)})
dev.off()