tmpaud

Disparity metrics over time and place

R

tmpaud(pred, grp = NULL, period = NULL, city = NULL, base = NULL)

The disparate impact ratio, the parity gap, the Gini coefficient of the groups’ shares flagged and the bias amplification score of fairdf(), for every city and period, and how far each city’s ratio moves over the periods (after Barman and Barman 2026).

Parameters

pred

The tool’s decisions: 1 (or TRUE) for a case it flags, 0 (or FALSE) otherwise, one per case. A clpre list from clprep() is taken too: its elements fill the arguments by name.

grp

Group labels: numbers, text or a factor, one per case, no missing values. Groups are ordered as the factor’s levels, or sorted.

period

The period of each case: labels (text, numbers or a factor), sorted as fair() sorts groups; ISO dates as text sort in time order.

city

NULL (one place, labelled "all"), or the city of each case: labels.

base

The base group: NULL for the group with the largest share flagged (the first in order on ties), its label, or its position from 1.

Returns

A list: cells, a data frame with one row per city and period that occurs: city, period, n, ok (TRUE when audited), di, dp, gini and bas (NaN when skipped); cities, one row per city: city, ncell (cells audited), di, dp, gini, bas (their means), dimin, dimax, dirng and ngt1; sum, rng (the largest range) and spread (largest minus smallest mean ratio of the cities; NaN with fewer than two); base.

Notes

A cell (one city in one period) is audited when it holds at least two groups and the base group; otherwise it is reported and skipped. The base group is the same in every cell: by default the group with the largest share flagged over all the data. For each city, the means of the four values over its audited cells (finite values only), the smallest and largest ratio, their range, and how many periods have a ratio above

• A ratio that moves a lot from one period to the next says that one audit at one time describes that time only; a spread between cities says the same tool can treat groups differently in different places. Neither says why. For intervals on one cell, call fairdf() on it.

Examples

set.seed(2)
n <- 600
g <- sample(c("a", "b"), n, TRUE)
per <- sample(c("2024-1", "2024-2", "2024-3"), n, TRUE)
cty <- sample(c("north", "south"), n, TRUE)
p <- rbinom(n, 1, ifelse(g == "a", 0.4, ifelse(cty == "north", 0.3, 0.2)))
tmpaud(p, g, per, cty)$cities

Also in the R reference, with the method and its source.