plot2.R

# R SCRIPT FOR CREATING PLOT.2

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# upload household power consumption file.
data<-read.table('household_power_consumption.txt', header =TRUE, sep=';')
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# optional -> brief data pre-analysis (df dimension and variable class)
dim(data);sapply(data,FUN=class) 
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# Change variables class to Date (column 1), or to numeric (columns 3 to 8)
data[,3:8] <- sapply(data[,3:8],as.numeric)
data[,1]<-as.Date(data[,1],'%d/%m/%Y') 
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# Select rows containing data between 2007-02-01 and 2007-02-02
data<-with(data, data[(Date >= "2007-02-01" & Date <= "2007-02-02"), ])
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# create vector with date+time columns, and then create a new variable 'Datetime' in data [class=POSIXct]
datetime <- paste(as.Date(data$Date), data$Time)
data$Datetime <- strptime(datetime, '%Y-%m-%d %H:%M:%S')
#---------------------------------------------------------------------------------
# Create png device, create line plot and close device
png(file='plot2.png', width = 480, height = 480, units = "px")
plot(data$Datetime, data$Global_active_power, type='l', xlab='', ylab='Global Active Power (kilowatts)')
dev.off()
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