# contr_code_helmert: Helmert code a factor In faux: Simulation for Factorial Designs

## Description

Helmert coding sets the grand mean as the intercept. Each contrast compares one level with the mean of previous levels.

## Usage

 `1` ```contr_code_helmert(fct, levels = NULL) ```

## Arguments

 `fct` the factor to contrast code (or a vector) `levels` the levels of the factor in order

## Value

the factor with contrasts set

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```df <- sim_design(between = list(pet = c("cat", "dog")), mu = c(10, 20), plot = FALSE) df\$pet <- contr_code_helmert(df\$pet) lm(y ~ pet, df) %>% broom::tidy() df <- sim_design(between = list(pet = c("cat", "dog", "ferret")), mu = c(2, 4, 9), empirical = TRUE, plot = FALSE) df\$pet <- contr_code_helmert(df\$pet) lm(y ~ pet, df) %>% broom::tidy() # reorder the levels to change the comparisons df\$pet <- contr_code_helmert(df\$pet, levels = c("dog", "cat", "ferret")) lm(y ~ pet, df) %>% broom::tidy() df\$pet <- contr_code_helmert(df\$pet, levels = c("ferret", "dog", "cat")) lm(y ~ pet, df) %>% broom::tidy() ```

faux documentation built on Sept. 14, 2021, 1:08 a.m.