R: Ratio Variable Creation

step_ratio {recipes} | R Documentation

## Ratio Variable Creation

### Description

`step_ratio` creates a a specification of a recipe step that will create one or more ratios out of numeric variables.

### Usage

    step_ratio(recipe, ..., role = "predictor", trained = FALSE,
      denom = denom_vars(), naming = function(numer, denom)
      make.names(paste(numer, denom, sep = "_o_")), columns = NULL,
      skip = FALSE)

    denom_vars(...)

    ## S3 method for class 'step_ratio'
    tidy(x, ...)

### Arguments

`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 in the numerator of the ratio. When used with `denom_vars`, the dots indicates which variables are used in the denominator. See `selections()` for more details. For the `tidy` method, these are not currently used.
`role` | For terms created by this step, what analysis role should they be assigned?. By default, the function assumes that the newly created ratios created by the original variables will be used as predictors in a model.
`trained` | A logical to indicate if the quantities for preprocessing have been estimated.
`denom` | A call to `denom_vars` to specify which variables are used in the denominator that can include specific variable names separated by commas or different selectors (see `selections()`). If a column is included in both lists to be numerator and denominator, it will be removed from the listing.
`naming` | A function that defines the naming convention for new ratio columns.
`columns` | The column names used in the ratios. This argument is not populated until `prep.recipe()` is executed.
`skip` | A logical. Should the step be skipped when the recipe is baked by `bake.recipe()`? While all operations are baked when `prep.recipe()` 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 = TRUE` as it may affect the computations for subsequent operations
`x` | A `step_ratio` object

### Value

An updated version of `recipe` with the new step added to the sequence of existing steps (if any). For the `tidy` method, a tibble with columns `terms` (the selectors or variables selected) and `denom`.

### Examples

    library(recipes)
    data(biomass)

    biomass$total <- apply(biomass[, 3:7], 1, sum)
    biomass_tr <- biomass[biomass$dataset == "Training",]
    biomass_te <- biomass[biomass$dataset == "Testing",]

    rec <- recipe(HHV ~ carbon + hydrogen + oxygen + nitrogen +
                        sulfur + total,
                  data = biomass_tr)

    ratio_recipe <- rec %>%
      # all predictors over total
      step_ratio(all_predictors(), denom = denom_vars(total)) %>%
      # get rid of the original predictors
      step_rm(all_predictors(), -ends_with("total"))

    ratio_recipe <- prep(ratio_recipe, training = biomass_tr)

    ratio_data <- bake(ratio_recipe, biomass_te)
    ratio_data

[Package recipes version 0.1.2 Index]