Responses to a Hadley tweet:
Is there an equivalent to https://t.co/erZb80L9YY for learning basic (bash) shell commands? (For someone who has never used shell before)
— Hadley Wickham (@hadleywickham) December 3, 2014The thing Hadley was pointing at https://try.github.io/
Erin Ledell suggested http://explainshell.com
Karl Broman suggested http://web.mit.edu/mprat/Public/web/Terminus/Web/main.html
| # library() or require() only load one package at a time | |
| # but... | |
| Packages <- c("dplyr", "ggplot2", "rstan", "readr") | |
| lapply(Packages, library, character.only = TRUE) | |
| # this loads as many as you put in 'Packages'. They need to be installed first, of course. |
1NF is the most basic of normal forms - each cell in a table must contain only one piece of information, and there can be no duplicate rows.
2NF and 3NF are all about being dependent on the primary key. Recall that a primary key can be made up of multiple columns. As Chris said in his response:
The data depends on the key [1NF], the whole key [2NF] and nothing but the key [3NF] (so help me [Codd][1]).
Say you have a table containing courses that are taken in a certain semester, and you have the following data:
Raymond Hettinger's professional at doing code review and architecture review
P vs. NP. Pythonic vs. Non-Pythonic.