faux (version 1.2.1)

add_contrast: Add a contrast to a data frame

Description

Add a contrast to a data frame

Usage

add_contrast(
  data,
  col,
  contrast = c("anova", "sum", "treatment", "helmert", "poly", "difference"),
  levels = NULL,
  ...,
  add_cols = TRUE,
  colnames = NULL
)

Value

the data frame with the recoded column and added columns (if add_cols == TRUE)

Arguments

data

the data frame

col

the column to recode

contrast

the contrast to recode to

levels

the levels of the factor in order

...

arguments to pass to the contrast function (base or omit)

add_cols

whether to just add the contrast to the existing column or also to create new explicit columns in the dataset (default)

colnames

optional list of column names for the added contrasts

Examples

df <- sim_design(between = list(time = 1:6), plot = FALSE) %>%
   add_contrast("time", "poly")

# test all polynomial contrasts
lm(y ~ time, df) %>% broom::tidy()

# test only the linear and quadratic contrasts
lm(y ~ `time^1` + `time^2`, df) %>% broom::tidy()