function to convert contrasts in factors to deviation coding

deviation_coding.R

library(tidyverse)

contrast_deviation <- function(vec_fct){
  new_contrast <- unique(vec_fct) %>% length() %>% contr.sum()
  contrasts(vec_fct) <- new_contrast
  vec_fct
}

# convert all char columns to factors that use deviation coding
mpg %>% 
  mutate_if(is.character, as.factor) %>% 
  mutate_if(is.factor, contrast_deviation)