R tips


quote from: http://ww2.coastal.edu/kingw/statistics/R-tutorials/formulae.html

symbol example meaning
+ + x include this variable
– x delete this variable
: x : z include the interaction between these variables
* x * z include these variables and the interactions between them
/ x / z nesting: include z nested within x
| x | z conditioning: include x given z
^ (u + v + w)^3 include these variables and all interactions up to three way
poly poly(x,3) polynomial regression: orthogonal polynomials
Error Error(a/b) specify the error term
I I(x*z) as is: include a new variable consisting of these variables multiplied
1 – 1 intercept: delete the intercept (regress through the origin)

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