Create Interaction VariablesSource:
step_interact creates a specification of a recipe
step that will create new columns that are interaction terms
between two or more variables.
step_interact( recipe, terms, role = "predictor", trained = FALSE, objects = NULL, sep = "_x_", skip = FALSE, id = rand_id("interact") )
A recipe object. The step will be added to the sequence of operations for this recipe.
A traditional R formula that contains interaction terms. This can include
.and selectors. See
selections()for more details, and consider using
tidyselect::starts_with()when dummy variables have been created.
For model terms created by this step, what analysis role should they be assigned? By default, the new columns created by this step from the original variables will be used as predictors in a model.
A logical to indicate if the quantities for preprocessing have been estimated.
A list of
termsobjects for each individual interaction.
A character value used to delineate variables in an interaction (e.g.
var1_x_var2instead of the more traditional
A logical. Should the step be skipped when the recipe is baked by
bake()? While all operations are baked when
prep()is run, some operations may not be able to be conducted on new data (e.g. processing the outcome variable(s)). Care should be taken when using
skip = TRUEas it may affect the computations for subsequent operations.
A character string that is unique to this step to identify it.
An updated version of
recipe with the new step added to the
sequence of any existing operations.
step_interact can create interactions between
variables. It is primarily intended for numeric data;
categorical variables should probably be converted to dummy
step_dummy() prior to being used for
Unlike other step functions, the
terms argument should
be a traditional R model formula but should contain no inline
log). For example, for predictors
C, a formula such as
~A:B:C can be used to make a three way interaction
between the variables. If the formula contains terms other than
(A+B+C)^3) only the interaction terms
are retained for the design matrix.
The separator between the variables defaults to "
that the three way interaction shown previously would generate a
A_x_B_x_C. This can be changed using the
When dummy variables are created and are used in interactions,
selectors can help specify the interactions succinctly. For
example, suppose a factor column
X gets converted to dummy
you wanted an interaction with numeric column
z, you could
create a set of specific interaction effects (e.g.
x_2:z + x_3:z and so on) or you could use
prep() evaluates this step,
starts_with("x_") resolves to
(x_2 + x_3 + x_4 + x_5 + x_6)
so that the formula is now
(x_2 + x_3 + x_4 + x_5 + x_6):z and
all two-way interactions are created.
tidy() this step, a tibble with column
terms (the interaction effects) is returned.
data(penguins, package = "modeldata") penguins <- penguins %>% na.omit() rec <- recipe(flipper_length_mm ~ ., data = penguins) int_mod_1 <- rec %>% step_interact(terms = ~ bill_depth_mm:bill_length_mm) # specify all dummy variables succinctly with `starts_with()` int_mod_2 <- rec %>% step_dummy(sex, species, island) %>% step_interact(terms = ~ body_mass_g:starts_with("species")) int_mod_1 <- prep(int_mod_1, training = penguins) int_mod_2 <- prep(int_mod_2, training = penguins) dat_1 <- bake(int_mod_1, penguins) dat_2 <- bake(int_mod_2, penguins) names(dat_1) #>  "species" "island" #>  "bill_length_mm" "bill_depth_mm" #>  "body_mass_g" "sex" #>  "flipper_length_mm" "bill_depth_mm_x_bill_length_mm" names(dat_2) #>  "bill_length_mm" "bill_depth_mm" #>  "body_mass_g" "flipper_length_mm" #>  "sex_male" "species_Chinstrap" #>  "species_Gentoo" "island_Dream" #>  "island_Torgersen" "body_mass_g_x_species_Chinstrap" #>  "body_mass_g_x_species_Gentoo" tidy(int_mod_1, number = 1) #> # A tibble: 1 × 2 #> terms id #> <chr> <chr> #> 1 bill_depth_mm:bill_length_mm interact_IUB7W tidy(int_mod_2, number = 2) #> # A tibble: 2 × 2 #> terms id #> <chr> <chr> #> 1 body_mass_g:species_Chinstrap interact_kM5w7 #> 2 body_mass_g:species_Gentoo interact_kM5w7