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plot2.R
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plot2.R
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#setwd("~/Coursera/ex_data_analysis")
# Coursera Exploratory Data Analysis Course Assignment 1
# Read data, subset it and reconstruct plots to match
# plot 2
# modify the data with linux cmd tools head, grep and cat to keep the header and filter for the 2 specified dates
# modified data is in GitHub repo
# set locale for R to display weekdays in english
Sys.setlocale("LC_TIME", "C");
# read data with character classes
data <- read.table(file="household_power_consumption_cut.txt", sep=";", header = TRUE, dec=".", stringsAsFactors=FALSE)
# parse date and time columns
data$datetime <- strptime(paste(data$Date, data$Time), "%e/%m/%Y %H:%M:%S")
# convert global active power to numeric values and save it as a new column
data$Global_active_powerNum <- as.numeric(data$Global_active_power)
# the initial subsetting did not work.
# subset the date
working <- data[data$Date %in% c("1/2/2007", "2/2/2007"), ]
# plot the output as a 480x480 png file
png(filename = "plot2.png",
width = 480, height = 480, units = "px", pointsize = 12,
bg = "white", res = 72, type="cairo")
plot(working$datetime,working$Global_active_powerNum, type="l", xlab="", ylab="Global Active Power (kilowatts)")
dev.off()