Cutting the Gordian Knot: The Moving-Average Type-Token Ratio (MATTR)

Type-token ratio (TTR), or vocabulary size divided by text length (V/N), is a time-honoured but unsatisfactory measure of lexical diversity. The problem is that the TTR of a text sample is affected by its length. We present an algorithm for rapidly computing TTR through a moving window that is independent of text length, and we demonstrate that this measurement can detect changes within a text as well as differences between texts.