Today

• Tidy data.

• Data transformation with dplyr.

Announcement

• HW1 is due Jan 26 @ 11:59pm.

• Quiz Import and Tidy Data due Feb 2 @ 11:59pm.

• HW2 is posted and due Feb 9 @ 11:59pm. (Start early. Ask questions on Slack or office hours.)

Q&A

• Want to enjoy the speed of data.table while using dplyr? Check out dtplyr.

• Q: R crashes and then I can never open it again. A: Locate the .RData file and delete it. Carefully inspect your code which may generate extremely large R objects causing the crash. Configure R to not save workspace as .RData on exit and not restore workspace on startup. R4DS recommendation: do not save R workspace as .RData on exit nor restore workspace on startup.