R: Create Counts of Patterns using Regular Expressions

step_count {recipes} | R Documentation

## Create Counts of Patterns using Regular Expressions

### Description

`step_count` creates a specification of a recipe step that will create a variable that counts instances of a regular expression pattern in text.

### Usage

    step_count(recipe, ..., role = "predictor", trained = FALSE,
      pattern = ".", normalize = FALSE, options = list(),
      result = make.names(pattern), input = NULL, skip = FALSE)

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

### Arguments

`recipe` | A recipe object. The step will be added to the sequence of operations for this recipe.
`...` | A single selector functions to choose which variable will be searched for the pattern. The selector should resolve into a single variable. See `selections()` for more details. For the `tidy` method, these are not currently used.
`role` | For a variable created by this step, what analysis role should they be assigned?. By default, the function assumes that the new dummy variable column created by the original variable will be used as a predictors in a model.
`trained` | A logical to indicate if the quantities for preprocessing have been estimated.
`pattern` | A character string containing a regular expression (or character string for `fixed = TRUE`) to be matched in the given character vector. Coerced by `as.character` to a character string if possible.
`normalize` | A logical; should the integer counts be divided by the total number of characters in the string?.
`options` | A list of options to `gregexpr()` that should not include `x` or `pattern`.
`result` | A single character value for the name of the new variable. It should be a valid column name.
`input` | A single character value for the name of the variable being searched. This is `NULL` until computed by `prep.recipe()`.
`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_count` 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 `result` (the new column name).

### Examples

    data(covers)

    rec <- recipe(~ description, covers) %>%
      step_count(description, pattern = "(rock|stony)", result = "rocks") %>%
      step_count(description, pattern = "famil", normalize = TRUE)

    rec2 <- prep(rec, training = covers)
    rec2

    count_values <- bake(rec2, newdata = covers)
    count_values

    tidy(rec, number = 1)
    tidy(rec2, number = 1)

[Package recipes version 0.1.2 Index]