title: Simcluster: clustering enumeration gene expression data on the simplex space.
abstract: BACKGROUND
  Transcript enumeration methods such as SAGE, MPSS, and sequencing-by-synthesis EST "digital northern", are important high-throughput techniques for digital gene expression measurement. As other counting or voting processes, these measurements constitute compositional data exhibiting properties particular to the simplex space where the summation of the components is constrained. These properties are not present on regular Euclidean spaces, on which hybridization-based microarray data is often modeled. Therefore, pattern recognition methods commonly used for microarray data analysis may be non-informative for the data generated by transcript enumeration techniques since they ignore certain fundamental properties of this space.
  
  
  RESULTS
  Here we present a software tool, Simcluster, designed to perform clustering analysis for data on the simplex space. We present Simcluster as a stand-alone command-line C package and as a user-friendly on-line tool. Both versions are available at: http://xerad.systemsbiology.net/simcluster.
  
  
  CONCLUSIONS
  Simcluster is designed in accordance with a well-established mathematical framework for compositional data analysis, which provides principled procedures for dealing with the simplex space, and is thus applicable in a number of contexts, including enumeration-based gene expression data.
authors.affiliation: Institute for Systems Biology, 1441 North 34th street, Seattle, WA 98103-8904, USA. rvencio@gmail.com
authors.forename: Ricardo Z N
authors.initials: RZ
authors.lastname: Vêncio
authors.forename: Leonardo
authors.initials: L
authors.lastname: Varuzza
authors.forename: Carlos A
authors.initials: CA
authors.lastname: de B Pereira
authors.forename: Helena
authors.initials: H
authors.lastname: Brentani
authors.forename: Ilya
authors.initials: I
authors.lastname: Shmulevich
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D016000:Cluster Analysis; D020869:Gene Expression Profiling / Q000379:methods*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D010363:Pattern Recognition, Automated; D011381:Programming Languages; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D014157:Transcription Factors