step_spatialsign {recipes} | R Documentation |
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", trained = FALSE, columns = NULL)
recipe |
A recipe object. The step will be added to the sequence of operations for this recipe. |
... |
One or more selector functions to choose which variables will be
used for the normalization. See |
role |
For model terms created by this step, what analysis role should they be assigned? |
trained |
A logical to indicate if the quantities for preprocessing have been estimated. |
columns |
A character string of variable names that will be (eventually)
populated by the |
The spatial sign transformation projects the variables onto a unit
sphere and is related to global contrast normalization. The spatial sign
of a vector w
is w/norm(w)
.
The variables should be centered and scaled prior to the computations.
An updated version of recipe
with the
new step added to the sequence of existing steps (if any).
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) 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)