circos

Circos is a software package for visualizing data in a circular layout, enabling the compact display of complex, multi-dimensional relationships across many categories. In genomics, Circos plots place genome ideograms around a circle and layer data in tracks such as histograms, heatmaps, and scatter plots, while links or chords can connect genomic regions to illustrate relationships like translocations, duplications, or conserved synteny between chromosomes.

Circos was developed by Martin Krzywinski and colleagues, and gained widespread attention with the 2009 Genome Biology paper Circos: An information aesthetic for comparative genomics. The project is distributed as open-source software, primarily written in Perl, and runs on POSIX-like systems. Outputs are typically vector graphics (SVG) or bitmap images, suitable for publication. Configuration is performed through plain-text files that describe ideograms, tracks, colors, scales, and links, with input data commonly provided in simple tab-delimited formats.

Typical use cases include visualizing chromosomal rearrangements, copy-number variation, and other large-scale genomic patterns, as well as comparative genomics across species. Beyond genomics, Circos has influenced the development of circular visualization styles in other domains and has inspired accompanying tools and web-based implementations that replicate or extend its circular paradigm.

Despite its powerful aesthetics, Circos can have a steep learning curve, requiring careful parameter tuning to produce readable plots. When properly configured, Circos remains a versatile and widely cited method for conveying complex relationships in a single, interpretable image.