title: InCHlib - interactive cluster heatmap for web applications.
abstract: BACKGROUND
  Hierarchical clustering is an exploratory data analysis method that reveals the groups (clusters) of similar objects. The result of the hierarchical clustering is a tree structure called dendrogram that shows the arrangement of individual clusters. To investigate the row/column hierarchical cluster structure of a data matrix, a visualization tool called 'cluster heatmap' is commonly employed. In the cluster heatmap, the data matrix is displayed as a heatmap, a 2-dimensional array in which the colour of each element corresponds to its value. The rows/columns of the matrix are ordered such that similar rows/columns are near each other. The ordering is given by the dendrogram which is displayed on the side of the heatmap.
  
  
  RESULTS
  We developedInCHlib(Interactive Cluster Heatmap Library), a highly interactive and lightweightJavaScriptlibrary for cluster heatmap visualization and exploration.InCHlibenables the user to select individual or clustered heatmap rows, to zoom in and out of clusters or to flexibly modify heatmap appearance. The cluster heatmap can be augmented with additional metadata displayed in a different colour scale. In addition, to further enhance the visualization, the cluster heatmap can be interconnected with external data sources or analysis tools. Data clustering and the preparation of the input file forInCHlibis facilitated by the Python utility scriptinchlib_clust.
  
  
  CONCLUSIONS
  The cluster heatmap is one of the most popular visualizations of large chemical and biomedical data sets originating, e.g., in high-throughput screening, genomics or transcriptomics experiments. The presentedJavaScriptlibraryInCHlibis a client-side solution for cluster heatmap exploration.InCHlibcan be easily deployed into any modern web application and configured to cooperate with external tools and data sources. ThoughInCHlibis primarily intended for the analysis of chemical or biological data, it is a versatile tool which application domain is not limited to the life sciences only.
authors.affiliation: Laboratory of Informatics and Chemistry, Faculty of Chemical Technology, Institute of Chemical Technology Prague, Technická 5, CZ-166 28 Prague, Czech Republic ; CZ-OPENSCREEN, Institute of Molecular Genetics of the ASCR, v. v. i, Vídeňská 1083, CZ-142 20 Prague, Czech Republic.
authors.forename: Ctibor
authors.initials: C
authors.lastname: Skuta
authors.affiliation: CZ-OPENSCREEN, Institute of Molecular Genetics of the ASCR, v. v. i, Vídeňská 1083, CZ-142 20 Prague, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Bartůněk
authors.affiliation: Laboratory of Informatics and Chemistry, Faculty of Chemical Technology, Institute of Chemical Technology Prague, Technická 5, CZ-166 28 Prague, Czech Republic ; CZ-OPENSCREEN, Institute of Molecular Genetics of the ASCR, v. v. i, Vídeňská 1083, CZ-142 20 Prague, Czech Republic.
authors.forename: Daniel
authors.initials: D
authors.lastname: Svozil
keywords: Big data; Client-side scripting; Cluster heatmap; Data clustering; Exploration; JavaScript library; Scientific visualization; Web integration