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plot3.R
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plot3.R
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# Read data file, which is expected to be in the current directory.
# Select data for just the two dates of interest.
# Replace '?' with NA everywhere in selected data.
# Create a new datetime column from the date and time columns.
# Convert the appropriate columns to numeric.
# return the resulting data frame
#
readit <- function() {
df <-read.csv("household_power_consumption.txt", sep=";", colClasses='character')
df2 <- df[(df$Date == '1/2/2007') | (df$Date == '2/2/2007'),]
df2[df2 == '?'] <- NA
df2$datetime <- paste(df2$Date, df2$Time)
df2$datetime <- strptime(df2$datetime, '%d/%m/%Y %H:%M:%S')
df2$Global_active_power <- as.numeric(df2$Global_active_power)
df2$Global_reactive_power <- as.numeric(df2$Global_reactive_power)
df2$Voltage <- as.numeric(df2$Voltage)
df2$Sub_metering_1 <- as.numeric(df2$Sub_metering_1)
df2$Sub_metering_2 <- as.numeric(df2$Sub_metering_2)
df2$Sub_metering_3 <- as.numeric(df2$Sub_metering_3)
df2
}
# Produce the third plot from the given data frame.
# Assume the caller set the device.
#
plot3 <- function(df2) {
plot(df2$datetime, df2$Sub_metering_1, type="n", xlab="", ylab="Energy sub metering")
lines(df2$datetime, df2$Sub_metering_1, type="l")
lines(df2$datetime, df2$Sub_metering_2, type="l", col="red")
lines(df2$datetime, df2$Sub_metering_3, type="l", col="blue")
legend("topright",legend=c('Sub_metering_1','Sub_metering_2','Sub_metering_3'), col=c('black','red', 'blue'), lty=c(1,1,1))
}
png("plot3.png", height=480, width=480)
plot3(readit())
dev.off()