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Exercise

Calculations with Times

Calculations using POSIXct objects are completely analogous to those using Date objects. Try to experiment with this code to increase or decrease POSIXct objects:

now <- Sys.time()
now + 3600          # add an hour
now - 3600 * 24     # subtract a day

Adding or subtracting time objects is also straightforward:

birth <- as.POSIXct("1879-03-14 14:37:23")
death <- as.POSIXct("1955-04-18 03:47:12")
einstein <- death - birth
einstein

You're developing a website that requires users to log in and out. You want to know what is the total and average amount of time a particular user spends on your website. This user has logged in 5 times and logged out 5 times as well. These times are gathered in the vectors login and logout, which are already defined in the workspace.

Instructions

100 XP
  • Calculate the difference between the two vectors logout and login, i.e. the time the user was online in each independent session. Store the result in a variable time_online.
  • Inspect the variable time_online by printing it.
  • Calculate the total time that the user was online. Print the result.
  • Calculate the average time the user was online. Print the result.