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Calculate Region Ratios

Source: R/feature-engineering.R
step_measure_ratios.Rd

step_measure_ratios() creates a specification of a recipe step that calculates ratios between integrated regions.

Usage

step_measure_ratios(
  recipe,
  numerator,
  denominator,
  name = NULL,
  method = c("trapezoid", "simpson"),
  measures = NULL,
  prefix = "ratio_",
  role = "predictor",
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("measure_ratios")
)

Arguments

recipe

A recipe object.

numerator

A numeric vector of length 2 specifying the numerator region.

denominator

A numeric vector of length 2 specifying the denominator region.

name

Output column name. If NULL, auto-generated from prefix.

method

Integration method: "trapezoid" (default) or "simpson".

measures

An optional character vector of measure column names.

prefix

Prefix for output column name if name is NULL. Default is "ratio_".

role

Role for generated column. Default is "predictor".

trained

Logical indicating if the step has been trained.

skip

Logical. Should the step be skipped when baking?

id

Unique step identifier.

Value

An updated recipe with the new step added.

Details

This step calculates the ratio of integrated areas between two regions: ratio = integral(numerator) / integral(denominator)

This is useful for calculating peak ratios in spectroscopy, or relative concentrations in chromatography.

If the denominator integral is zero or NA, the ratio will be NA.

See also

Other measure-features: step_measure_bin(), step_measure_integrals(), step_measure_moments()

Examples

library(recipes)

rec <- recipe(water + fat + protein ~ ., data = meats_long) |>
  update_role(id, new_role = "id") |>
  step_measure_input_long(transmittance, location = vars(channel)) |>
  step_measure_ratios(
    numerator = c(1, 30),
    denominator = c(70, 100),
    name = "low_high_ratio"
  ) |>
  prep()

bake(rec, new_data = NULL)
#> # A tibble: 215 × 6
#>       id water   fat protein .measures low_high_ratio
#>    <int> <dbl> <dbl>   <dbl>    <meas>          <dbl>
#>  1     1  60.5  22.5    16.7 [100 × 2]          0.824
#>  2     2  46    40.1    13.5 [100 × 2]          0.839
#>  3     3  71     8.4    20.5 [100 × 2]          0.896
#>  4     4  72.8   5.9    20.7 [100 × 2]          0.882
#>  5     5  58.3  25.5    15.5 [100 × 2]          0.800
#>  6     6  44    42.7    13.7 [100 × 2]          0.829
#>  7     7  44    42.7    13.7 [100 × 2]          0.841
#>  8     8  69.3  10.6    19.3 [100 × 2]          0.821
#>  9     9  61.4  19.9    17.7 [100 × 2]          0.824
#> 10    10  61.4  19.9    17.7 [100 × 2]          0.828
#> # ℹ 205 more rows