exposure: Exposure Index
In arthurgailes/rsegregation: Calculate Empirical Measures of Segregation

Description Usage Arguments Details Value Note Source

View source: R/two_group_measures.R

The summation is over all the geographic units, e. g. census tracts, comprising the larger geographic entity for which the exposure index is being calculated.

1	exposure(group1, group2, population = NA, summed = TRUE, na.rm = TRUE)

`group1`	Numeric vectors representing the proportions of each group in each observation
`group2`	Numeric vectors representing the proportions of each group in each observation
`population`	A vector of population totals for each row, or weights summing to a total of one. If NA, will assume all populations/weights are equal. Set to 1 to silence warning. If a string, will use the string as the named column of the dataframe provided in ...
`summed`	If TRUE, will return a single summary statistic. (Or one value per group if specifying `dplyr::group_by`.) If FALSE (default), will return a vector equaling the length of the input vectors. If 'weighted' (only for divergence and information theory), returns a vector as in FALSE, but with pre-weighted values, such that `sum(divergence(..., summed = 'weighted))` is equivalent to `divergence(..., summed = T)`.
`na.rm`	logical. Should missing values (including NaN) be removed? Used only if `summed` is set to TRUE.

The maximum value of the exposure index is the percent in the second group. That is, if blacks make up 30 percent of the population of a metropolis, the maximum value of the average percent black for white residents of that metropolis will be 30 percent. This will require that the index of dissimilarity measuring the evenness with which blacks and every other racial group are distributed across the metropolis equals zero. The minimum value of the exposure index is zero. That is, although blacks might make up 30 percent of a metropolis, whites could live in exclusively white neighborhoods. If the exposure index equals zero, than the index of dissimilarity comparing those two groups will equal zero. The exposure index involves two mutually exclusive racial groups. However, the average percent black in the census tract of the typical white in a metropolis is almost always different from the average percent white for the typical black living in the same metropolis.

The formula for exposure is Σ (g1/G1)*(g2/t), where g1=group1, G1=sum(group1),g2=group2, and t=totalPop

A scalar value, see note.

Setting summed == FALSE will return by-observation measures, but this measure is not meant to be decomposed. These results are for verification purposes only.

Wendell Bell, A Probability Model for the Measurement of Ecological Segregation, Social Forces, Volume 32, Issue 4, May 1954, Pages 357–364, https://doi.org/10.2307/2574118

arthurgailes/rsegregation documentation built on May 23, 2021, 6:33 a.m.