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Dilution Factor Correction

Source: R/dilution-correction.R
step_measure_dilution_correct.Rd

step_measure_dilution_correct() creates a specification of a recipe step that corrects concentration values by applying dilution factors. This is essential when samples are diluted during preparation and need to be back-calculated to original concentrations.

Usage

step_measure_dilution_correct(
  recipe,
  ...,
  dilution_col = "dilution_factor",
  operation = c("multiply", "divide"),
  handle_zero = c("error", "warn", "skip"),
  role = NA,
  trained = FALSE,
  skip = FALSE,
  id = recipes::rand_id("measure_dilution_correct")
)

Arguments

recipe

A recipe object.

...

One or more selector functions to choose feature columns (concentration values) to correct. If empty, all numeric columns (excluding metadata columns) will be selected.

dilution_col

Name of the column containing dilution factors. Default is "dilution_factor".

operation

How to apply the dilution factor:

  • "multiply" (default): concentration * dilution_factor (back-calculate from diluted to original concentration)

  • "divide": concentration / dilution_factor (apply dilution)

handle_zero

How to handle zero dilution factors:

  • "error" (default): Stop with an error

  • "warn": Warn and set result to NA

  • "skip": Silently set result to NA

role

Not used by this step.

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

Dilution Factor Interpretation

The dilution factor represents how much the sample was diluted:

  • A factor of 1 means no dilution (undiluted)

  • A factor of 2 means 1:2 dilution (1 part sample + 1 part diluent)

  • A factor of 10 means 1:10 dilution

Back-Calculation

When using operation = "multiply" (the default): original_concentration = measured_concentration * dilution_factor

This corrects for the dilution to get the true concentration in the original sample.

When to Use

Use this step after quantitation (calibration) when samples were diluted to bring concentrations within the calibration range.

See also

step_measure_surrogate_recovery(), measure_calibration_predict()

Other calibration: measure_matrix_effect(), step_measure_standard_addition(), step_measure_surrogate_recovery()

Examples

library(recipes)

# Example: samples diluted to fit calibration range
data <- data.frame(
  sample_id = paste0("S", 1:6),
  dilution_factor = c(1, 2, 5, 10, 1, 1),
  analyte = c(50, 45, 42, 48, 51, 49)  # Measured after dilution
)

rec <- recipe(~ ., data = data) |>
  update_role(sample_id, new_role = "id") |>
  step_measure_dilution_correct(
    analyte,
    dilution_col = "dilution_factor",
    operation = "multiply"
  ) |>
  prep()

# Back-calculated concentrations
bake(rec, new_data = NULL)
#> # A tibble: 6 × 3
#>   sample_id dilution_factor analyte
#>   <chr>               <dbl>   <dbl>
#> 1 S1                      1      50
#> 2 S2                      2      90
#> 3 S3                      5     210
#> 4 S4                     10     480
#> 5 S5                      1      51
#> 6 S6                      1      49
# S1: 50*1=50, S2: 45*2=90, S3: 42*5=210, S4: 48*10=480