Log-likelihood-ratio cost — cllr • crimlab

Scores a set of likelihood ratios against the truth. Ratios from same-source comparisons should be large and ratios from different-source comparisons small. The cost is 1 for a system that always answers 1. It is above 0 for any set of ratios, and tends to 0 as the ratios of a system that separates the two kinds perfectly grow without bound. See proof("cllr") and cllrmin().

Usage

cllr(same, diff)

Arguments

same: Likelihood ratios from same-source comparisons: positive numbers.
diff: Likelihood ratios from different-source comparisons: positive numbers.

Value

One number, the cost in bits.

References

Brummer, N. and du Preez, J. (2006). Application-independent evaluation of speaker detection. Computer Speech and Language, 20(2-3), 230-275. doi:10.1016/j.csl.2005.08.001

Examples

cllr(same = c(50, 200, 8), diff = c(0.01, 0.2, 1.5))
#> [1] 0.3008346