ExData_Plotting1/plot2.R at master · evgaster/ExData_Plotting1 · GitHub

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rawDataFileName <- "../household_power_consumption.txt"

# Read the data from the file.
# For now keep the date and time as a  character strings.
d <- read.table(rawDataFileName,
                header = TRUE,
                sep = ";",
                na.strings = "?",
                colClasses = c("character",
                               "character",
                               "numeric",
                               "numeric",
                               "numeric",
                               "numeric",
                               "numeric",
                               "numeric",
                               "numeric"
                ),
                comment.char = ""
)

# Keep only the needed dates.
# The dates appear to be in the D/M/YYYY format,
# without leading zeros.
d <- subset(d, Date %in% c("1/2/2007", "2/2/2007"))

# Convert the Date and Time character strings to a timestamp.
d$Timestamp <- as.POSIXct(paste(d$Date, d$Time, sep = " "),
                          format = "%d/%m/%Y %H:%M:%S")
# Drop the Date and Time character strings.
d <- d[, ! names(d) %in% c("Date", "Time")]

# Draw the Global_active_power over time.
png("plot2.png")
plot(d$Timestamp, d$Global_active_power,
     type = "l",
     xlab = "",
     ylab = "Global Active Power (kilowatts)"
     )
dev.off()