Generic for setting contrasts, primarily intended for internal use.
Usage
use_contrasts(
factor_col,
code_by = NA,
reference_level = NA,
set_intercept = NA,
drop_trends = NA,
labels = NULL,
as_is = FALSE,
...
)Arguments
- factor_col
The factor column to use, eg data$gender
- code_by
Either a matrix or a function
- reference_level
The level to use as the reference level, default NA
- set_intercept
The intercept to use, default NA
- drop_trends
Whether to drop trends, default NA
- labels
Labels to use in the contrast matrix, must equal number of contrasts
- as_is
Logical, default FALSE, whether to suppress auto switching of the reference level to the first level if not specified
- ...
Additional arguments to be passed to use_contrast_function, specifically, which level you want the reference level to be
Examples
# Create a contrast matrix given some factor vector with the specified
# reference level
use_contrasts(gl(5,2), sum_code, reference_level = 3)
#> 1 2 4 5
#> 1 1 0 0 0
#> 2 0 1 0 0
#> 3 -1 -1 -1 -1
#> 4 0 0 1 0
#> 5 0 0 0 1
# Set column labels; order for labels is the same as the column indices
use_contrasts(gl(3,2), scaled_sum_code, labels = c("2-1", "3-1"))
#> 2-1 3-1
#> 1 -0.3333333 -0.3333333
#> 2 0.6666667 -0.3333333
#> 3 -0.3333333 0.6666667
my_data <- mtcars
my_data$gear <- factor(mtcars$gear)
MASS::fractions(use_contrasts(my_data$gear, helmert_code))
#> 4 5
#> 3 -1/2 -1/3
#> 4 1/2 -1/3
#> 5 0 2/3