plot3..R

library(dplyr)
data_set <- data.table::fread('household_power_consumption.txt', na.strings='?')
#get datetime objects
data_set <- data_set %>% mutate( date_time = as.POSIXct(paste(data_set$Date, data_set$Time),
                                                        format = '%d/%m/%Y %H:%M:%S'))
# set Global_active_power to numeric
data_set <- data_set %>% mutate(Global_active_power = as.numeric(Global_active_power))
# select dates
data_set <- data_set %>% filter(date_time > '2007-02-01' & date_time < '2007-02-03')
png('plot3.png')
# sub_metering_1
with(data_set, plot(date_time, Sub_metering_1, type='l', xlab='', ylab='Energy sub metering'))
# sub_metering_2
with(data_set, lines(date_time, Sub_metering_2, col = 'red'))
# sub_metering_3
with(data_set, lines(date_time, Sub_metering_3, col = 'blue'))
# add legend
legend('topright', c('Sub_metering_1', 'Sub_metering_2', 'Sub_metering_3'), col=c('black', 'red', 'blue'),
       lty = c(1,1,1))
dev.off()