Spatial Sign PreprocessingSource:
step_spatialsign() is a specification of a recipe step that will convert
numeric data into a projection on to a unit sphere.
step_spatialsign( recipe, ..., role = "predictor", na_rm = TRUE, trained = FALSE, columns = NULL, skip = FALSE, id = rand_id("spatialsign") )
A recipe object. The step will be added to the sequence of operations for this recipe.
One or more selector functions to choose variables for this step. See
selections()for more details.
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: should missing data be removed from the norm computation?
A logical to indicate if the quantities for preprocessing have been estimated.
A character string of the selected variable names. This field is a placeholder and will be populated once
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.
The spatial sign transformation projects the variables
onto a unit sphere and is related to global contrast
normalization. The spatial sign of a vector
The variables should be centered and scaled prior to the computations.
tidy() this step, a tibble with column
terms (the columns that will be affected) is returned.
This step performs an unsupervised operation that can utilize case weights.
As a result, only frequency weights are allowed. For more
information, see the documentation in case_weights and the examples on
Unlike most, this step requires the case weights to be available when new
samples are processed (e.g., when
bake() is used or
predict() with a
workflow). To tell recipes that the case weights are required at bake time,
recipe %>% update_role_requirements(role = "case_weights", bake = TRUE).
update_role_requirements() for more information.
Serneels, S., De Nolf, E., and Van Espen, P. (2006). Spatial sign preprocessing: a simple way to impart moderate robustness to multivariate estimators. Journal of Chemical Information and Modeling, 46(3), 1402-1409.
data(biomass, package = "modeldata") biomass_tr <- biomass[biomass$dataset == "Training", ] biomass_te <- biomass[biomass$dataset == "Testing", ] rec <- recipe( HHV ~ carbon + hydrogen + oxygen + nitrogen + sulfur, data = biomass_tr ) ss_trans <- rec %>% step_center(carbon, hydrogen) %>% step_scale(carbon, hydrogen) %>% step_spatialsign(carbon, hydrogen) ss_obj <- prep(ss_trans, training = biomass_tr) transformed_te <- bake(ss_obj, biomass_te) plot(biomass_te$carbon, biomass_te$hydrogen) plot(transformed_te$carbon, transformed_te$hydrogen) tidy(ss_trans, number = 3) #> # A tibble: 2 × 2 #> terms id #> <chr> <chr> #> 1 carbon spatialsign_Geidk #> 2 hydrogen spatialsign_Geidk tidy(ss_obj, number = 3) #> # A tibble: 2 × 2 #> terms id #> <chr> <chr> #> 1 carbon spatialsign_Geidk #> 2 hydrogen spatialsign_Geidk