InCHlib - interactive cluster heatmap for web applications.

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 developed (Interactive Cluster Heatmap Library), a highly interactive and lightweight library for cluster heatmap visualization and exploration. enables 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 for is facilitated by the Python utility script .

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 presented library is a client-side solution for cluster heatmap exploration. can be easily deployed into any modern web application and configured to cooperate with external tools and data sources. Though is 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.