contr_code_sum {faux}

Sum code a factor

Description

Sum coding sets the grand mean as the intercept. Each contrast compares one level with the grand mean.

Usage

contr_code_sum(fct, levels = NULL, omit = length(levels))

Arguments

fct

the factor to contrast code (or a vector)

levels

the levels of the factor in order

omit

the level to omit (defaults to the last level)

Value

the factor with contrasts set

Examples

df <- sim_design(between = list(pet = c("cat", "dog", "bird", "ferret")), 
                 mu = c(2, 4, 9, 13), empirical = TRUE, plot = FALSE)

df$pet <- contr_code_sum(df$pet)
lm(y ~ pet, df) %>% broom::tidy()

df$pet <- contr_code_sum(df$pet, omit = "cat")
lm(y ~ pet, df) %>% broom::tidy()

df$pet <- contr_code_sum(df$pet, omit = 1)
lm(y ~ pet, df) %>% broom::tidy()