raw_polynomial_code {contrastable} | R Documentation |
Raw Polynomial code
Description
Make raw polynomial contrast, rather than orthogonal ones. Normally you would use orthogonal polynomials, so make sure this is what you want. Using raw polynomials may increase the collinearity in your model, especially with higher numbers of levels.
Usage
raw_polynomial_code(n)
Arguments
n |
Integer umber of factor levels to compute contrasts for. |
Details
For n levels of factors where k in 1:n, generate a matrix with n-1
comparisons where each comparison looks for a polynomial trend of degree k,
where each polynomial may be correlated with the others. Normally you would
use orthogonal polynomials, see stats::contr.poly()
and
orth_polynomial_code()
Value
A contrast matrix with dimensions n rows and (n-1) columns.
Examples
mydf <- data.frame(
grp = rep(c("a", "b", "c", "d"), each = 2000),
val = c(
rnorm(200, 2, 1),
rnorm(200, 5, 1),
rnorm(200, 7.5, 1),
rnorm(200, 15, 1)
)
) |>
set_contrasts(grp ~ raw_polynomial_code)
stats::lm(val ~ grp, data = mydf)
[Package contrastable version 1.0.2 Index]