Dyadic offending rates

Offences by one group against another, as a rate per member of the offending group and as a rate per offender-victim pair exposed. The rate per offender rises with the size of the victim group even when offenders choose victims at random; the rate per pair does not. See proof("dyadrt").

Usage

dyadrt(count, pop)

Arguments

count

A square matrix (or 2-d table) of offence counts, offending group in rows and victim group in columns: non-negative numbers. When it names both its rows and its columns, the columns are matched to the rows by name, and both to pop when pop is named.

pop

Group sizes: positive numbers, as a numeric vector, a 1-d table, a list of single numbers or a one-row data frame. Unnamed, they are taken in the order of the rows: only names protect against a mismatch.

Value

A data frame with one row per dyad: off, vic, count, rtoff, rtpair, nulloff (the rate per offender under random mixing) and ratio (rtpair over the pooled pair rate; 1 under random mixing).

Examples

pop <- c(a = 800, b = 200)
dyadrt(count = outer(pop, pop) / 1000, pop = pop)
#>   off vic count rtoff rtpair nulloff ratio
#> 1   a   a   640   0.8      1     0.8     1
#> 2   b   a   160   0.8      1     0.8     1
#> 3   a   b   160   0.2      1     0.2     1
#> 4   b   b    40   0.2      1     0.2     1