Check for Unsystematic Data Violations

Checks a data set against the two Johnson and Bickel (2008) criteria for unsystematic delay-discounting data:

• Criterion 1: Any subsequent value of y exceeds the previous value by more than a specified proportion of the larger later reward (ll).

• Criterion 2: The last value of y is not at least a specified proportion of ll less than the first value of y (a decline of exactly c2 * ll passes).

Usage

check_unsystematic(dat, ll = 1, c1 = 0.2, c2 = 0.1)

Arguments

dat

A data frame containing the delay-discounting data. It must have at least two columns:

• id: A unique identifier for the data set.

• y: The indifference points to be analyzed.

• x (optional): Delay values; when present, each subject's points are ordered by delay first.

Missing y or x values and duplicate delays within a subject are errors.

ll

A numeric value representing the larger later reward, in the same units as y. Default is 1 (indifference points expressed as a proportion of the larger later reward). Both thresholds are applied on the y scale (c1 * ll and c2 * ll), so amount-scale data (e.g. y in dollars) need ll set to the larger later amount.

c1

A numeric value for the threshold proportion for Criterion 1. Default is 0.2.

c2

A numeric value for the threshold proportion for Criterion 2. Default is 0.1.

Value

A tibble with the following columns:

• id: The unique identifier for the data set.

• c1_pass: Logical value indicating whether Criterion 1 was passed.

• c2_pass: Logical value indicating whether Criterion 2 was passed.

Details

The criteria are applied separately to each id, so a data frame containing several subjects returns one row per subject. When an x (delay) column is present, each subject's points are ordered by delay before the criteria are applied.

Examples

data <- tibble::tibble(
  id = c(rep("P1", 6)),
  x = c(1, 7, 30, 90, 180, 365), # delays
  y = c(0.9, 0.5, 0.3, 0.2, 0.1, 0.05) # indifference points
)
check_unsystematic(data, ll = 1, c1 = 0.2, c2 = 0.1)
#> # A tibble: 1 × 3
#>   id    c1_pass c2_pass
#>   <chr> <lgl>   <lgl>  
#> 1 P1    TRUE    TRUE