Inverse Document Frequency (IDF): A Measure of Deviations from Poisson
Low frequency words tend to be rich in content, and vice versa. But not all equally frequent words are equally meaningful. We will use inverse document frequency (IDF), a quantity borrowed from Information Retrieval, to distinguish words like somewhat and boycott. Both somewhat and boycott appeared approximately 1000 times in a corpus of 1989 Associated Press articles, but boycott is a better keyword because its IDF is farther from what would be expected by chance (Poisson).
KeywordsInformation Retrieval Word Frequency Hide Variable Inverse Document Frequency Poisson Mixture
Unable to display preview. Download preview PDF.
- Church, K. and Gale, W. 1997. Poisson Mixtures. Natural Language Engineering, vol 3 (2).Google Scholar
- Johnson, N. and Kotz, S. 1969. Discrete Distributions Houghton Mifflin, Boston, Ma.Google Scholar
- Katz, S. M. 1996. Distribution of content words and phrases in text and language modelling. in Natural Language Engineering, vol 2(1), pp. 15–59.Google Scholar
- Mosteller, F. and Wallace, D. 1964. Inference and Disputed Authorship: The Federalist. Addison-Wesley, Reading, Ma.Google Scholar
- Salton, G. 1989. Automatic Text Processing. Addison-Wesley, Reading, Ma.Google Scholar
- Shannon, C. 1948. The Mathemarical Theory of Communication. in Bell System Technical Journal Google Scholar
- Sparck Jones, K. 1972. A Statistical Interpretation of Term Specificity and its Application in Retrieval. in Journal of Documentation, vol. 28 (1), pp. 11–21.Google Scholar
- van Rijsbergen, C. 1979. Information Retrieval. Second edition. Butterworths, London.Google Scholar