Finding frequent items in data streams

Moses Charikar, Kevin Chen, Martin Farach-Colton

Research output: Contribution to journalConference articlepeer-review

300 Scopus citations


We present a 1-pass algorithm for estimating the most frequent items in a data stream using limited storage space. Our method relies on a data structure called a COUNT SKETCH, which allows us to reliably estimate the frequencies of frequent items in the stream. Our algorithm achieves better space bounds than the previously known best algorithms for this problem for several natural distributions on the item frequencies. In addition, our algorithm leads directly to a 2-pass algorithm for the problem of estimating the items with the largest (absolute) change in frequency between two data streams. To our knowledge, this latter problem has not been previously studied in the literature.

Original languageEnglish (US)
Pages (from-to)3-15
Number of pages13
JournalTheoretical Computer Science
Issue number1
StatePublished - Jan 26 2004
EventAutomata, Languages and Programming - Malaga, Spain
Duration: Jul 8 2002Jul 13 2002

All Science Journal Classification (ASJC) codes

  • Theoretical Computer Science
  • Computer Science(all)


  • Approximation
  • Frequent items
  • Streaming algorithm


Dive into the research topics of 'Finding frequent items in data streams'. Together they form a unique fingerprint.

Cite this