Frequency list

In computational linguistics, a frequency list is a sorted list of words (word types) together with their frequency, where frequency here usually means the number of occurrences in a given corpus. A short example could be:

the 3789654
he 2098762
[...]
king 57897
boy 56975
[...]
outragious [sic] 76
[...]
stringyfy 5
[...]
transducionalify 1

It seems that Zipf's law holds for frequency lists drawn from longer texts of any natural language. Frequency lists are a necessary prerequisite for building of an electronic dictionary, which is by itself a prerequisite for a wide range of applications in computational linguistics.

German linguists define the häufigkeitsklasse (frequency class) N of an item in the list using the base 2 logarithm of the ratio between its frequency and the frequency of the most frequent item. The most common item belongs to frequency class 0 (zero) and any item that is approximately half as frequent belongs in class 1. In the example list above, the misspelled word outragious has a ratio of 76/3789654 and belongs in class 16.

N=\left\lfloor0.5-\log_2\left(\frac{\text{Frequency of this item}}{\text{Frequency of most common item}}\right)\right\rfloor

where \lfloor\ldots\rfloor is the floor function.

Frequency lists, together with semantic networks, are used to identify the least common, specialized terms to be replaced by their hypernyms in a process of semantic compression.

References

See also