## what is cheat sheet
[https://en.wikipedia.org/wiki/Cheat_sheet](https://en.wikipedia.org/wiki/Cheat_sheet)
A cheat sheet (also cheatsheet) or crib sheet is a concise set of notes used for quick reference.
Cheat sheets are so named because they may be used by students without the instructor's knowledge to cheat on a test. However, at higher levels of education where rote memorization is not as important as in basic education, students may be permitted to consult their own notes (crib notes, or crib sheet) during the exam (which is not considered cheating). The act of preparing a crib sheet can be an educational exercise, and students are sometimes only allowed to use crib sheets they have written themselves.
https://www.rstudio.com/resources/cheatsheets/#contributed-cheatsheets
https://github.com/rstudio/cheatsheets/raw/master/powerpoints/0-template.pptx
http://kaiwu.city/index.php/downloads?task=download.send&id=5&catid=3&m=0
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